Research activity information

• Blood biomarkers of occupational exposure to emamectin benzoate among farmers in Phitsanulok, Thailand
  Theerayut Baubhom; Nontiya Homkham; Aksorn Saengtienchai; Yared B. Yohannes; Shouta M. M. Nakayama; Mayumi Ishizuka; Yoshinori Ikenaka; Brian T. Buckley; Saowanee Norkaew
  JOURNAL OF HAZARDOUS MATERIALS ADVANCES, 22, May 2026
  English, Scientific journal
• An Initial Survey of Targeted Anticancer Drug Residues in Municipal Wastewater of Bangkok, Thailand
  Aksorn Saengtienchai; Yared Beyene Yohannes; Somkiat Sreebun; Yoshinori Ikenaka; Shouta M. M. Nakayama; Mayumi Ishizuka; Usuma Jermnak
  ENVIRONMENTS, 13, 5, 25 Apr. 2026
  English, Scientific journal
• Reductive dominance and limited cytochrome P450 activity in neonicotinoid metabolism by elephant liver microsomes
  Kanami Watanabe; Kraisiri Khidkhan; Aksorn Saengtienchai; Chaleamchat Somgrid; Patcharapa Towiboon; Taweepoke Angkawanish; Warangkhana Langkaphin; Kittikul Namwongprom; Narueporn Kittisirik; Yared B. Yohannes; Yoshinori Ikenaka; Shouta M. M. Nakayama; Mayumi Ishizuka
  JOURNAL OF VETERINARY MEDICAL SCIENCE, 88, 4, 607, 613, Apr. 2026
  English, Scientific journal
• Intergenerational sex-specific transcriptomic alterations in gonads of mice after parental lead exposure
  Nelly Banda; Kanami Watanabe; John Yabe; Rio Doya; Yared Beyene Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Shouta M. M. Nakayama
  REPRODUCTIVE TOXICOLOGY, 140, Mar. 2026
  English, Scientific journal
• Exploring the intricacies of indoor dust pollution from neonicotinoid insecticides and its human health impacts: An exemplar from eleven agricultural communities in Ghana, West Africa.
  Collins Nimako; Osei Akoto; Nathaniel Boadi; Prince Ofori; Yared B Yohannes; Shouta M M Nakayama; Yoshinori Ikenaka; Mayumi Ishizuka
  Journal of hazardous materials, 500, 140172, 140172, 05 Dec. 2025, [International Magazine]
  English, Scientific journal, Neonicotinoid insecticides are the most widely used class of insecticides globally; however, knowledge of their indoor residual pollution is limited across various regions of the world. This study aimed to investigate the intricacies of indoor dust contamination from neonicotinoid insecticides across 11 agrarian communities in Ghana, West Africa, and to assess the potential human health risks. Settled indoor dust samples were collected from 430 households and subjected to a Liquid Chromatography-Mass Spectrometry/Mass Spectrometry analysis. Following analysis, 10 neonicotinoid compounds and 6 neonicotinoid metabolites were detected, with the following frequency trend: imidacloprid and its 5 associated metabolites (Σ6IMI; detection frequency = 99.07 %) > acetamiprid compounds (Σ2ACE; detection frequency = 93.72 %) > thiamethoxam (89.53 %) > clothianidin (82.09 %) > sulfoxaflor (74.19 %) > imidaclothiz (4.88 %) > thiacloprid (4.42 %) > flupyradifurone (3.95 %) > dinotefuran (3.72 %) > nitenpyram (2.33 %). The median concentrations were as follows: imidacloprid (0.145 µg/g) > thiamethoxam (0.03 µg/g) > acetamiprid (0.014 µg/g) > sulfoxaflor (0.003 µg/g) > clothianidin (0.002 µg/g). Upon exposure assessment, the daily intakes of neonicotinoids were highest in younger populations compared to older ones, with the following values: toddlers (3338118 pg/kg/bw), infants (2677255 pg/kg/bw), children (1072966 pg/kg/bw), teenagers (74368 pg/kg/bw), and adults (53120 pg/kg/bw). However, the maximum hazard quotients for neonicotinoids across all age groups were below 1. Overall, the current study shows extensive indoor contamination by neonicotinoids in the target Ghanaian communities. Although hazard quotients are below unity, the high exposure potentials, especially for children, indicates a need for further toxicological evaluation and long-term environmental health surveillance.
• Evaluation of ascorbic acid as an intervention of metal toxicity in dogs in Kabwe district.
  Nelly Banda; Mahongo Selwa; Rio Doya; Nyein Chan Soe; Andrew Kataba; John Yabe; Golden Zyambo; Kaampwe Muzandu; Yared Beyene Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Shouta Mm Nakayama
  Veterinary and animal science, 30, 100519, 100519, Dec. 2025, [International Magazine]
  English, Scientific journal, Non-essential metals and metalloids are known to induce oxidative stress in exposed organisms, often leading to cellular damage and systemic toxicity. While chelation therapy remains the primary treatment for metal toxicity, its application is limited by side effects. L-ascorbic acid (L-AA), a widely available antioxidant, has emerged as a promising nutritional intervention for mitigating metal-induced oxidative stress. Dogs, whose blood lead levels (BLLs) closely mirror those of humans, have been utilized as sentinel species in environmental toxicology studies. This study aimed to evaluate the therapeutic potential of L-AA in dogs residing in Kabwe, Zambia, a former mining town where remediation of heavy metal contamination is ongoing. The reported BLLs in Kabwe dogs ranged from 0.43 µg/dL to 123.5 µg/dL. A total of 22 dogs (10 females and 12 males) received oral L-AA supplementation daily for 14 days. Blood samples were collected on Day 1 of L-AA administration and Day 14 to assess biochemical and toxicological changes. Post-treatment analysis revealed statistically significant reductions in plasma malondialdehyde, cortisol, blood urea nitrogen, and creatinine levels, as determined by Student's t-test and Wilcoxon signed-rank test. Additionally, δ-aminolaevulinic acid dehydratase activity was significantly elevated, indicating improved oxidative status. These findings support the efficacy of L-AA in attenuating oxidative stress associated with metal and metalloid exposure, even in the absence of exposure cessation. Interestingly, Pb levels declined predominantly in dogs younger than 24 months. Furthermore, reductions in Zn and Cu commonly linked to L-AA administration were observed exclusively in male dogs, suggesting a sex-specific response.
• Evaluation of neurotoxicity of neonicotinoid insecticides using lipidomics.
  Tomoya Koike; Anri Hirai; Kei Nomiyama; Akihumi Eguchi; Nobuhiko Hoshi; Tetsushi Hirano; Collins Nimako; Yared Beyene Yohannes; Mai Tamba; Shouta M M Nakayama; Mayumi Ishizuka; Yoshinori Ikenaka
  Environmental toxicology and chemistry, 44, 11, 3212, 3224, 01 Nov. 2025, [International Magazine]
  English, Scientific journal, Neonicotinoid (NN) pesticides are widely used globally, but recent studies suggest that even nontoxic doses can induce anxiety-like behaviors and alter brain monoamine neurotransmitter levels in mice. Current neurotoxicity assays may fail to detect subtle toxic effects, such as higher brain function abnormalities caused by small molecule disruptions. These findings highlight the need for highly sensitive and reproducible neurotoxicity testing methods. The brain, a lipid-rich organ, relies on lipids for various functions, and disturbances in lipid homeostasis are linked to numerous diseases. This study uses lipidomics to analyze the cerebral cortex of mice exposed to the NN acetamiprid (ACE), aiming to identify lipid biomarkers of neurotoxicity. Thirty 12-week-old male C57BL/6J mice were randomly divided into control (0 mg/kg), low dose (65 mg/kg), and high dose (130 mg/kg) groups, with 10 mice in each group. Mice were euthanized, and cerebral cortex samples were collected 30 min after oral ACE administration. Lipids were extracted and analyzed using liquid chromatography-quadrupole time-of-flight mass spectrometry. A total of 358 lipids were annotated. Fifteen lipids exhibited a fold-change > 2.0 and significant differences between control and high-dose groups, with an area under the curve ≥ 0.900 in receiver operating characteristic analysis. Increased levels of seven fatty acids (FAs; e.g., palmitic acid) and five fatty acyl esters of hydroxy FAs (e.g., FAHFA 22:6_22:5) were observed, suggesting roles in neurodegenerative diseases and inflammation. These findings identify a promising lipid biomarker linked to NN-induced neurotoxicity and contribute to detecting neurotoxic effects from acute exposure to such substances.
• Anthropogenic Activities Elevate Heavy Metals Levels in Soil and Tree Bark; A Case Study of Lower Zambezi and Mosi-Oa-Tunya National Parks.
  Nelly Banda; Kanami Watanabe; Rio Doya; Nyein Chan Soe; Andrew Kataba; John Yabe; Golden Zyambo; Kaampwe Muzandu; Yared Beyene Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Shouta M M Nakayama
  Archives of environmental contamination and toxicology, 89, 2, 180, 194, Aug. 2025, [International Magazine]
  English, Scientific journal, The impact of various human activities on protected environments remains a significant concern. Mining for ores is crucial in many aspects of society. To achieve global decarbonisation, more metals are required, which will lead to increased worldwide metal exploration and mining. Zambia is primarily a mining country and has expanded exploration into protected lands (national parks). The effects of this exploration on these protected areas is ongoing. This study aimed to establish baseline data for monitoring metal pollution in the Lower Zambezi National Park before mining commenced. It also evaluated whether tourism influenced metal pollution in national parks and how these metals and metalloids correlate within tree bark and soils. To accomplish this, soil and Acacia tree bark samples were collected from Lower Zambezi National Park and Mosi-Oa-Tunya National Park. Arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were analysed in this study. The concentrations of metals and metalloids were higher in areas with vehicular traffic and mining activity in the national parks, which may directly impact the biosystems in those areas. Maximum levels of metals in soil in these areas were as follows: As 40.8 mg/kg, Cd 0.879 mg/kg, Cr 241 mg/kg, Hg 1.1 mg/kg, Pb 211 mg/kg, and Zn 1285 mg/kg. When compared to areas of lower anthropogenic activities, differences in metal concentrations were up to 1000-fold. These changes can potentially affect the adaptation of wildlife to various stressors, especially as we are facing global climate change.
• Pollution and partitioning of neonicotinoid insecticides in free-grazing ducks and their eggs: Implications for human health.
  Collins Nimako; Kraisiri Khidkhan; Sittinee Kulprasertsri; Saranya Poapolathep; Paphatsara Khunlert; Yared B Yohannes; Yoshinori Ikenaka; Shouta M M Nakayama; Mayumi Ishizuka; Amnart Poapolathep
  Environmental pollution (Barking, Essex : 1987), 373, 126099, 126099, 20 Mar. 2025, [International Magazine]
  English, Scientific journal, Neonicotinoid insecticides are used extensively in many pest control schemes across the globe; but little is known about their impacts on free-grazing domestic birds and the quality of meat or eggs produced from such birds. This study assessed the pollution and partitioning of neonicotinoids in serum and eggs of free-grazing ducks from 5 provinces of Thailand and elucidated the associated human health implications. Biological samples (duck serum, egg albumins, and egg yolks) and environmental samples (soil, water, feed) were collected from 9 duck farms in Thailand and subjected to LC/MS/MS analysis. Out of 6 neonicotinoid compounds targeted, five were detected in duck serum. Imidacloprid had the greatest median concentration of 1.4 ng/mL and the highest detection frequency (df) of 85.8 % in the ducks' serum, followed by acetamiprid (median concentration = 0.4 ng/mL; df = 2.8 %), clothianidin (median concentration = 0.2 ng/mL; df = 9.4 %) or thiamethoxam (median concentration = 0.2 ng/mL; df = 7.5 %) and dinotefuran (only one sample was contaminated with 6.3 ng/mL of dinotefuran). The neonicotinoids were similarly detected in soil, water, and feed samples obtained from the duck farms, suggesting that the ducks were exposed to the insecticides from the nearby agricultural fields. The neonicotinoid compounds selectively accumulated in the albumin of duck eggs compared to yolk. The median concentration ratios of albumin to yolk obtained for imidacloprid, dinotefuran, thiamethoxam, clothianidin, and acetamiprid were 694, 463, 458, 382, and 263, respectively. However, upon human health risk analysis, levels of neonicotinoids detected in duck eggs were not found to present any appreciable risks to duck egg consumers.
• Neonicotinoid detection in rainwater in Japan
  Zanne Sandriati PUTRI; Toshiko SATO; Yared Beyene YOHANNES; Yoshinori IKENAKA; Masumi YAMAMURO
  Environmental Monitoring and Contaminants Research, 5, 57, 65, Japan Society for Environmental Chemistry, 2025
  Scientific journal
• Anticoagulant rodenticide accumulation in the liver and plasma of pigeons (Columba livia) in Thailand.
  Kosal Phourng; Ratiwan Sitdhibutr; Yared Beyene Yohannes; Yoshinori Ikenaka; Aksorn Saengtienchai
  Open veterinary journal, 15, 8, 3608, 3617, 2025, [International Magazine]
  English, Scientific journal, BACKGROUND: Anticoagulant rodenticides (ARs) are widely used worldwide to control rodents. Currently, many countries are considering the use of ARs, which results in widespread accumulation and poisoning of nontarget animals. Nontarget pigeons (Columba livia) typically live near human communities and agricultural areas. These birds are at high risk of accidental daily exposure to ARs. AIM: This study aimed to evaluate ARs in the liver and plasma of pigeons living in rural and urban areas of Thailand. METHODS: Bird samples were characterized by sampling location, age, body weight (BW), and body condition score. Liver and plasma samples were extracted using liquid-liquid extraction with diethyl ether and analyzed for coumatetralyl and warfarin by liquid chromatography-mass spectrometry. RESULTS: Coumatetralyl and warfarin were detected in pigeons from both rural and urban areas. Both subadult and adult birds showed the presence of these two compounds, which were mainly detected in rural areas. The increase in BW was compared with the accumulation of coumatetralyl and warfarin, and a significant difference was observed. In addition, the concentration of coumatetralyl was significantly higher in the liver than in the plasma. The plasma concentrations of coumatetralyl and warfarin were 0.19-0.50 and 0.12-2.41 ng/ml, respectively. In the liver, coumatetralyl levels were higher than those of warfarin, with concentrations ranging from 0.07- to 3.33-ng/g wet weight and from 0.12- to 0.50-ng/g wet weight. CONCLUSION: AR use in human settlements and agricultural areas poses a high risk of accumulation in nontarget animals, such as pigeons. The findings of this study indicate coumatetralyl and warfarin in various concentrations in pigeon hepatic and plasma samples.
• Forensic detection and quantification of methomyl in animal stomach contents using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS) in Japan
  Yared Beyene YOHANNES; Aki TANAKA; Yuko KIHARA; Tsuyoshi TAJIMA; Shouta NAKAYAMA; Collins NIMAKO; Yoshinori IKENAKA; Mayumi ISHIZUKA
  Journal of Veterinary Medical Science, Japanese Society of Veterinary Science, 2025
  Scientific journal
• Sex dependent intergenerational effects of lead in mouse model.
  Nelly Banda; Nyein Chan Soe; John Yabe; Rio Doya; Yared Beyene Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Shouta M M Nakayama
  Scientific reports, 14, 1, 30233, 30233, 04 Dec. 2024, [International Magazine]
  English, Scientific journal, Lead (Pb) exposure negatively impacts fertility in both males and females, pregnancy outcomes, and child brain development. We investigated the reproductive and neurological effects of Pb exposure on male and female mice via Pb-contaminated soil for 4 weeks. Breeding was conducted after completion of exposure, in four groups; group 1 consisted of exposed dams and unexposed sires, group 2 consisted of exposed sires and unexposed dams, group 3 consisted of exposed sires and exposed dams and group 4 was the control. Generally, Pb exposure reduced observed conception rates, with a cumulative decrement observed when both males and females are exposed. Gene expression of the testes revealed oxidative stress as the cause of reduced conception rates. Neurological tests: Morris water maze and rotarod were conducted on F1 generation offspring. Maternally and paternally exposed F1 mice performed poorly in the Morris water maze when compared to the control. The severity of the neurological effects was also parent-dependent and sex-dependent. Paternal Pb exposure effects were more pronounced in female offspring. A comparison of gene expression changes of the hippocampus and prefrontal cortex showed paternal Pb-exposure resulted in more prefrontal cortex changes than in the hippocampus, a trend also recorded in the exposed sires. The pronounced effects in female offspring of paternal Pb exposure may suggest that Pb neurological effects may be X-chromosome-linked.
• 鳥類アミノレブリン酸脱水酵素の鉛曝露に対する感受性の比較
  丸山 瑞貴; 渡邊 有希子; 石井 千尋; 齊藤 慶輔; 牛根 奈々; 伊藤 真輝; 飯間 裕子; 中谷 裕美子; 長嶺 隆; 銅谷 理緒; 小笠原 浩平; 池中 良徳; Yohannes Yared Beyene; 石塚 真由美; 中山 翔太
  日本野生動物医学会誌, 29, Suppl., 141, 142, 日本野生動物医学会, Dec. 2024
  Japanese
• 沖縄島の希少固有種であるヤンバルクイナにおける抗凝固系殺鼠剤の感受性評価
  小間 隆央; 小出 将士; 近藤 充希; 森田 鮎子; 中谷 裕美子; 長嶺 隆; 久保田 彰; Yohannes Yared Beyene; 池中 良徳; 石塚 真由美; 中山 翔太
  日本野生動物医学会誌, 29, Suppl., 142, 142, 日本野生動物医学会, Dec. 2024
  Japanese
• Effect of Java plum (Syzygium cumini) leave extract and a silver nanoparticles synthesis on pathogens in skin diseases of dogs.
  Namthip Wongstitwilairoong; Usuma Jermnark; Napasorn Paochoosak; Orawan Limsivilai; Wissanuwat Chimnoi; Yared Beyene Yohannes; Yoshinori Ikenaka; Aksorn Saengtienchai
  Open veterinary journal, 14, 10, 2662, 2677, Oct. 2024, [International Magazine]
  English, Scientific journal, BACKGROUND: Antibiotic use has been rising in both humans and animals. The growing concern over antimicrobial drug resistance and the promotion of regional drug use have led to a rise in the interest in medicinal applications of herbs combined with biosynthesized nanoparticles. AIM: To evaluate the antimicrobial and acaricidal effects of Syzygium cumini leaves crude extract (Sc-CE) and biosynthesized S. cumini silver nanoparticles (Sc-AgNPs) on dog skin pathogens and determined the optimal concentration and time for in vitro application. METHODS: Syzygium cumini leaves (Sc) were prepared as Sc-CE and Sc-AgNPs. The biosynthesized silver nanoparticles were characterized employing various techniques, including dynamic light scattering, scanning electron microscopy, and energy-dispersive X-ray analysis. Phytochemical analyses were conducted using liquid chromatography coupled with quadrupole time-of-flight mass spectrometry screening. Antimicrobial activity was examined against gram-positive bacteria, including Staphylococcus aureus and Staphylococcus pseudintermedius, gram-negative bacteria such as Pseudomonas aeruginosa, yeast strains including Malassezia pachydermatis and Candida albicans, and ectoparasite. Cytotoxicity was evaluated on canine primary dermal fibroblast (CPDF) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. RESULTS: The Sc-AgNPs exhibited nanoparticle sizes ranging from 100 to 350 nm with aggregated spherical shape and contained Ag element in this nanoparticle. Myricetin and Phloretin were among the extracted compounds, contributing to the reduction of pathogenic organisms. Sc-AgNPs showed high efficacy against skin pathogens compared to Sc-CE, with a lower cytotoxicity effect on CPDF. CONCLUSION: The Sc-AgNPs demonstrated superior efficiency against pathogens in dog skin diseases as both concentration- and time-dependent and were deemed safe to CPDF within 24 hours.
• Characterization of Neonicotinoid Metabolites by Cytochrome P450-Mediated Metabolism in Poultry.
  Adisorn Dam-On; Collins Nimako; Sittinee Kulprasertsri; Yoshinori Ikenaka; Yared B Yohannes; Shouta M M Nakayama; Mayumi Ishizuka; Saranya Poapolathep; Amnart Poapolathep; Kraisiri Khidkhan
  Toxics, 12, 8, 21 Aug. 2024, [International Magazine]
  English, Scientific journal, Neonicotinoids, a neuro-effective class of insecticides, are heavily applied in agricultural activities worldwide. Poultry can be exposed to neonicotinoids by several routes, but the knowledge of neonicotinoid's metabolism in poultry and its associated interspecies differences is highly limited. Hence, this study aims to investigate the species differences in metabolite formations, as well as cytochrome P450 (CYP)-dependent metabolism of four major neonicotinoid compounds, acetamiprid, imidacloprid, clothianidin, and thiamethoxam, in poultry. In vitro biotransformation assays using hepatic microsomes of chicken, ducks, geese, quails, and rats were conducted. Metabolites of neonicotinoids were then screened by LC/Q-TOF and quantified by LC/MS/MS. The results revealed an existence of interspecies differences in the formations of N-, low PbAc-ZnAc [12 mg/kg PbAc (3 mg PbAc/rat/day) + 0.2 mg ZnAc/rat/48 hr], high PbAc [120 mg/kg (30 mg PbAc/rat/day)], and high PbAc-ZnAc [120 mg/kg (30 mg PbAc/rat/day) + 1 mg ZnAc/rat/48 hr] for 8 weeks. A significant reduction in body weight gain was observed in the high PbAc group relative to the control group. Muscles and testes both had reduced and increased Pb uptake in low PbAc-ZnAc and high PbAc-ZnAc groups compared to PbAc only groups, respectively. Bone Pb levels in the high PbAc-ZnAc group were lower than the high PbAc group. Zinc co-administration attenuated Pb-induced inhibition of delta aminolaevulinic acid dehydratase enzyme and enhanced catalase enzyme activity at a high level of exposure. Moreover, ZnAc seems to have minimized the effects of Pb-induced mRNA dysregulation in antioxidant and antiapoptotic enzymes encoding genes. Heme oxygenase-1 was downregulated in the kidney and brain in the low PbAc group. Liver glutathione peroxidase and thioredoxin reductase-1 were downregulated in the high PbAc group. These findings suggest that zinc co-administration with lead may partially mitigate against Pb-induced toxicities.
• Glutathione S-transferase gene polymorphisms in association with susceptibility to lead toxicity in lead- and cadmium-exposed children near an abandoned lead-zinc mining area in Kabwe, Zambia.
  Yared Beyene Yohannes; Shouta M M Nakayama; John Yabe; Haruya Toyomaki; Andrew Kataba; Hokuto Nakata; Kaampwe Muzandu; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Environmental science and pollution research international, 29, 5, 6622, 6632, 28 Aug. 2021, [International Magazine]
  English, Scientific journal, Interindividual genetic variations determine human's susceptibility to heavy metal-induced toxicity. Thus, we analyzed blood concentrations of lead (Pb) and cadmium (Cd) in 140 lead-exposed children. Genotyping of the glutathione S-transferase (GST) genes, GSTM1, GSTT1, and GSTP1 genes, was carried out to investigate their possible association with heavy metal concentrations and the risk of susceptibility to Pb toxicity. Exposure to both heavy metals was prevalent among the children. The blood Pb level ranged from 3.30 to 74.0 μg dL-1 with an average value of 26.8 μg dL-1 that is five times above its reference level. The average Cd level (0.22 μg L-1) was below its reference level. The metal-gene interaction showed positive correlation between GSTT1 null genotype and Pb and Cd levels (β = 0.11; p = 0.02 and β = 0.10; p = 0.01, respectively). More pronounced effects (β = 0.19; p < 0.01 and β = 0.25; p = 0.04) were found for the mixture of the three putative genes with blood Pb concentration. The susceptibility analysis using 10 μg dL-1 as blood Pb cutoff level showed a high risk of Pb toxicity (OR = 2.54; 95% CI: 1.02-6.32, p = 0.04) for children carrying the GSTP1 Ile/Val genotype. Further, the combined effect of GSTP1 Ile/Val with GSTT1 null genotype was more pronounced and showed an increased risk of susceptibility to Pb toxicity (OR = 11.7; 95% CI: 1.36-102.1, p = 0.02). In summary, this study suggests that GSTT1 null and GSTP1 Ile/Val genotypes are the main genetic factors, and individual and specific combinations of GSTP1 Ile/Val with GSTM1 and GSTT1 GST polymorphisms are associated with susceptibility to Pb toxicity.
• Bioaccumulation of DDT and other organochlorine pesticides in amphibians from two conservation areas within malaria risk regions of South Africa.
  Nico J Wolmarans; Lieven Bervoets; Ruan Gerber; Yared Beyene Yohannes; Shouta Mm Nakayama; Yoshinori Ikenaka; Mayumi Ishizuka; Patrick Meire; Nico J Smit; Victor Wepener
  Chemosphere, 274, 129956, 129956, Jul. 2021, [International Magazine]
  English, Scientific journal, The threat to wildlife from chemical exposure exists regardless of the presence of conservation boundaries. An issue exacerbated by the use of environmentally persistent insecticides for vector control and long-range transport of legacy persistent organic pollutants. In this comparative study between two important conservation regions in South Africa, Kruger National Park (KNP) and Ndumo Game Reserve (NGR), we assessed organochlorine pesticide (OCP) accumulation in several anuran species collected from within the conservation regions. The two conservation regions differ in size and subsequent proximity of collection sites to OCP input sources. Detectable concentrations of OCPs were present in ∼ half the frogs analysed from KNP and ∼all frogs from NGR and total OCP loads were similar between regions, where measured in the same species. The OCP profiles in KNP frogs were representative of legacy pesticides likely introduced via long-range transport, whereas NGR profiles showed influence of current use of DDT consistent with close proximity to sources. This indicates amphibians can accumulate OCPs within conservation regions and that the exposure of non-target organisms inside conservation regions to current use pesticides has a strong association with proximity to sources. These results serve to inform conservation management decision making with regard to the non-target organism effects of chemical interventions such as vector control pesticide use in and around conservation regions.
• Assessment of LeadCare® II analysis for testing of a wide range of blood lead levels in comparison with ICP-MS analysis.
  Hokuto Nakata; Shouta M M Nakayama; John Yabe; Kaampwe Muzandu; Haruya Toyomaki; Yared Beyene Yohannes; Andrew Kataba; Golden Zyambo; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Chemosphere, 271, 129832, 129832, May 2021, [International Magazine]
  English, Scientific journal, The LeadCare® testing system, which utilizes anodic stripping voltammetry (ASV) methodology, has been widely used worldwide for cost-effective blood lead level (BLL) screening. However, some concerns have recently been issued regarding inaccurate results obtained using LeadCare®. Hence, we aimed to evaluate the accuracy of BLL measured by LeadCare® II (BLLLC) by comparison with ICP-MS (BLLIM) by the Passing-Bablok regression, Deming regression, and Bland-Altman analyses by using 994 venous blood samples. BLLLC ranged from 3.3 to 162.3 μg/dL, while BLLIM ranged from 0.8 to 154.8 μg/dL. Although BLLLC and BLLIM exhibited a strong and positive correlation, BLLLC values were generally greater than BLLIM values, indicative of the overestimation of the LeadCare® analysis. A large positive bias of 19.15 ± 8.26 μg/dL and 29.25 ± 14.04 μg/dL for BLLLC compared with BLLIM were recorded in the BLLLC range of 45.0-64.9 μg/dL and for ≥65.0 μg/dL, respectively. In contrast, a bias of ≤0.3 μg/dL was observed at a BLLLC of less than 10.0 μg/dL. Blood copper, cadmium, and iron levels did not exhibit an effect on the bias of BLLLC, indicative of the minimal potential interferences of the metals; these interferences are a cause for concern with the ASV method. In conclusion, LeadCare® analysis is thought to be a good tool for screening purposes at a lower BLL around the reference level of 5 μg/dL in the initial stage; however, conversion or retesting using a laboratory analyzer is recommended at a higher BLL for appropriate clinical evaluation and research.
• Levels of DDTs and other organochlorine pesticides in healthy wild Nile crocodiles (Crocodylus niloticus) from a flagship conservation area
  Ruan Gerber; Hindrik Bouwman; Danny Govender; Mayumi Ishizuka; Yoshinori Ikenaka; Yared B. Yohannes; Nico J. Smit; Victor Wepener
  Chemosphere, 264, Pt 1, 128368, 128368, Elsevier BV, Feb. 2021, [International Magazine]
  English, Scientific journal, Mass Nile crocodile (Crocodylus niloticus) deaths in Africa's premier conservation area, the Kruger National Park (KNP), prompted numerous studies to determine possible causes of the sudden die-offs. The majority highlighted the involvement of the anthropocene to crocodile mass mortalities. One of the potential causative agents was identified as legacy compounds such as organochlorine pesticides (OCPs) present in the various aquatic ecosystems of the KNP. Thus, this study aimed to quantify OCP levels in wild crocodiles from the aquatic systems associated with the KNP. As part of a larger study, muscle tissue samples were collected from tails of 12 wild crocodiles. Results indicated that eight of the 19 OCPs analysed for were quantifiable. These included DDTs (2130-167968 ng/g lw), chlordanes (BD - 7583 ng/g lw) and cyclodeines (BD - 872 ng/g lw). Measured concentrations indicated spatial- and sex-related differences in accumulation patterns. DDT and its metabolites, paricularly p,p'-DDE accumulated to the highest concentrations of the OCP groups. Levels of the different groups of OCPs were the highest recorded in recent history from any crocodilian tissue. The different measured OCP residues were between 2.5 and 120 times higher than levels reported in literature, depending on the compound. These results are of ecotoxicological significance and have several management implications. In view of individuals being sampled from a conservation area it emphasizes the fact that pollutants know no boundaries and that premier conservation areas such as the world renowned KNP may be some of the most contaminated areas of the world.
• Delta-aminolevulinic acid dehydratase (ALAD) and vitamin D receptor (VDR) genes polymorphisms in children residing in an abandoned lead‑zinc mine area in Kabwe, Zambia
  Yared B. Yohannes; Shouta M.M. Nakayama; John Yabe; Haruya Toyomaki; Andrew Kataba; Hokuto Nakata; Kaampwe Muzandu; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Meta Gene, 27, 100838, 100838, Feb. 2021
  English, Scientific journal
• An Investigation of the Wild Rat Crown Incisor as an Indicator of Lead (Pb) Exposure Using Inductively Couple Plasma Mass Spectrometry (ICP-MS) and Laser Ablation ICP-MS.
  Andrew Kataba; Shouta M M Nakayama; Hokuto Nakata; Haruya Toyomaki; Yared B Yohannes; John Yabe; Kaampwe Muzandu; Golden Zyambo; Ayano Kubota; Takehisa Matsukawa; Kazuhito Yokoyama; Yoshinori Ikenaka; Mayumi Ishizuka
  International journal of environmental research and public health, 18, 2, 18 Jan. 2021, [International Magazine]
  English, Scientific journal, Lead (Pb) is a metal toxicant of great public health concern. The present study investigated the applicability of the rat incisor in Pb exposure screening. The levels of lead in teeth (Pb-T) in the crown and root of incisors in laboratory Pb-exposed Sprague Dawley rats were quantified using inductively coupled plasma mass spectrometry (ICP-MS). The crown accumulated much Pb-T than the root of the Sprague Dawley rat incisor. The levels of lead in blood (Pb-B) were positively correlated with the Pb-T in the crown and root incisors of the Sprague Dawley rats. As an application of the Pb-T crown results in experimental rats, we subsequently analyzed the Pb-T in the crown incisors of Pb-exposed wild rats (Rattus rattus) sampled from residential sites within varying distances from an abandoned lead-zinc mine. The Pb-T accumulation in the crown of incisors of R. rattus rats decreased with increased distance away from the Pb-Zn mine. Furthermore, the Pb-T was strongly correlated (r = 0.85) with the Pb levels in the blood. Laser ablation ICP-MS Pb-T mappings revealed a homogenous distribution of Pb in the incisor with an increased intensity of Pb-T localized in the tip of the incisor crown bearing an enamel surface in both Sprague Dawley and R. rattus rats. These findings suggest that Pb-T in the crown incisor may be reflective of the rat's environmental habitat, thus a possible indicator of Pb exposure.
• Evaluation of the ameliorative effect of Spirulina (Arthrospira platensis) supplementation on parameters relating to lead poisoning and obesity in C57BL/6J mice
  Nakata Hokuto; Nakayama Shouta M.M.; Kataba Andrew; Kataba Andrew; Yohannes Yared Beyene; Yohannes Yared Beyene; Ikenaka Yoshinori; Ikenaka Yoshinori; Ishizuka Mayumi
  Journal of Functional Foods, 77, 2021, [Peer-reviewed]
• Clinical biochemical parameters associated with the exposure to multiple environmental metals in residents from Kabwe, Zambia.
  Hokuto Nakata; Shouta M M Nakayama; John Yabe; Kaampwe Muzandu; Haruya Toyomaki; Yared Beyene Yohannes; Andrew Kataba; Golden Zyambo; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Chemosphere, 262, 127788, 127788, Jan. 2021, [International Magazine]
  English, Scientific journal, Lead (Pb) interferes with various bodily functions. Although high blood Pb (Pb-B) levels in residents from Kabwe, Zambia have been reported, the accumulation pattern of other metals remains unknown. The study was designed to determine the Pb-B, blood cadmium (Cd-B), and zinc (Zn-B) values of 504 representative samples from Kabwe, as well as the potential associated adverse health effects. The Pb-B level ranged from 0.79 to 154.75 μg/dL and generally increased in areas near the mine. A significant elevation of Cd-B was observed in two areas (0.37 ± 0.26 and 0.32 ± 0.30 μg/L) where the two highest mean Pb-B levels were recorded. By contrast, the Zn-B values did not differ greatly with respect to area. Some blood biochemical parameters relating to hepatic and renal functions were out of the normal range in approximately 20-50% of studied adult participants. The δ-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly inhibited in the two areas contaminated by Pb and Cd. A significant negative relationship was observed between metal levels and clinical parameters, e.g., between Pb-B and δ-ALAD for all the age categories and between Cd-B and the estimated glomerular filtration rate for all the age categories except 0-4 years. The elevated Cd-B in areas near the mine relative to the other areas suggested the potential adverse health effects of Cd and/or the interaction of Pb and Cd. A significant association of metal levels with clinical parameters also indicated the effects of metal exposure on hematopoietic, hepatic, and renal systems.
• Acute exposure to environmentally relevant lead levels induces oxidative stress and neurobehavioral alterations in larval zebrafish (Danio rerio).
  Andrew Kataba; Tarryn L Botha; Shouta M M Nakayama; Yared B Yohannes; Yoshinori Ikenaka; Victor Wepener; Mayumi Ishizuka
  Aquatic toxicology (Amsterdam, Netherlands), 227, 105607, 105607, Oct. 2020, [International Magazine]
  English, Scientific journal, The ubiquitous contamination of environmental lead (Pb) remains a worldwide threat. Improper Pb mine waste disposal from an abandoned lead-zinc mine has recently unearthed widespread Pb poisoning in children in Kabwe Zambia. Although the adverse effects of Pb on human health have begun to receive attention, the ecotoxicological effects on aquatic vertebrates still need further investigation. In addition, there is paucity in the knowledge on the behavioural and molecular subcellular responses in larval zebrafish exposed to Pb within the range of environmental relevant concentration (average 3 μg/L with maximum of 94 μg/L) on aquatic organisms such as zebrafish. The adverse effects of environmentally relevant levels of Pb on larval zebrafish was evaluated by measuring swimming behaviour under alternating dark and light conditions. Larval zebrafish acutely exposed to environmentally relevant Pb exhibited neuro-behavioural alteration including enhanced hyperactivity under light conditions evidenced by increased distanced covered and speed compared to the control. The alteration of entire behavioral profiles was further associated with the disturbed expression patterns of mRNA level of key genes associated with antioxidant (HO-1, Ucp-2 and CoxI), proapoptotic gene (TP53), and antiapoptotic gene (Bcl-2). To our knowledge, this is the first report on the effects of environmentally relevant Pb levels from Kabwe, Zambia and their adverse neurobehavioural effects and subcellular molecular oxidative responses in larval zebrafish acutely exposed within a 30 min period. The current results would be beneficial in our understanding of the effects of low Pb levels acutely discharged into an aquatic environment and the life of aquatic organisms.
• Blood lead levels and aberrant DNA methylation of the ALAD and p16 gene promoters in children exposed to environmental-lead.
  Yared B Yohannes; Shouta Mm Nakayama; John Yabe; Hokuto Nakata; Haruya Toyomaki; Andrew Kataba; Kaampwe Muzandu; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Environmental research, 188, 109759, 109759, 05 Jun. 2020, [Peer-reviewed], [International Magazine]
  English, Scientific journal, BACKGROUND: Lead (Pb) is a well-known toxic heavy metal which can have serious public health hazards. As of today, there is no safe threshold for Pb exposure, especially for children. Lead exposure has been associated with adverse health outcomes involving epigenetic mechanisms, such as aberrant DNA methylation. The objective of the present study was to elucidate the associations between blood lead levels (BLLs) and gene-specific promoter DNA methylation status in environmental Pb-exposed children from Kabwe, Zambia. METHODS: A cross-sectional study was conducted using 2 to 10-year-old children from high Pb exposed area (N = 102) and low Pb exposed area (N = 38). We measured BLLs using a LeadCare II analyzer and investigated the methylation status of the ALAD and p16 gene promoters by methylation-specific PCR. RESULTS: The mean BLLs were 23.7 μg/dL and 7.9 μg/dL in high Pb exposed and low Pb exposed children, respectively. Pb exposure was correlated with increased methylation of the ALAD and p16 genes. The promoter methylation rates of ALAD and p16 in high Pb exposed children were 84.3% and 67.7%, and 42.1% and 44.7% in low Pb exposed children, respectively. Significantly increased methylation was found in both genes in high Pb exposed children compared with low Pb exposed children (p < 0.05). Children with methylated ALAD and p16 genes showed an increased risk of Pb poisoning (odd ratio >1) compared to the unmethylated status. CONCLUSIONS: This study for the first time tries to correlate promoter methylation status of the ALAD and p16 genes in environmental Pb-exposed children from Kabwe, Zambia as a representative. The result suggests that Pb exposure increases aberrations in ALAD and p16 gene methylation, which may be involved in the mechanism of Pb toxicity.
• Land Use in Habitat Affects Metal Concentrations in Wild Lizards Around a Former Lead Mining Site.
  Rio Doya; Shouta Mm Nakayama; Hokuto Nakata; Haruya Toyomaki; John Yabe; Kaampwe Muzandu; Yared B Yohannes; Andrew Kataba; Golden Zyambo; Takahiro Ogawa; Yoshitaka Uchida; Yoshinori Ikenaka; Mayumi Ishizuka
  Environmental science & technology, 54, 22, 14474, 14481, 03 Jun. 2020, [Peer-reviewed], [International Magazine]
  English, Scientific journal, We investigated the potential effects of different land use and other environment factors on animals living in a contaminated environment. The study site in Kabwe, Zambia, is currently undergoing urban expansion, while lead contamination from former mining activities is still prevalent. We focused on a habitat-generalist lizards (Trachylepis wahlbergii). The livers, lungs, blood and stomach contents of 224 lizards were analyzed for their lead, zinc, cadmium, copper, nickel and arsenic concentrations. Habitat types were categorized based on vegetation data obtained from satellite images. Multiple regression analysis revealed that land use categories of habitats and three other factors significantly affected lead concentrations in the lizards. Further investigation suggested that the lead concentrations in lizards living in bare fields were higher than expected based on distance from the contaminant source, while those in lizards living in green fields were lower than expected. In addition, lead concentration of lungs were higher than that of liver in 19% of the lizards, implying direct exposure to lead via dust inhalation besides digestive exposure. Since vegetation reduces the production of dust from surface soil, it is plausible that dust from the mine is one of the contamination sources, and that vegetation can reduce exposure to this.
• Current trends of blood lead levels, distribution patterns and exposure variations among household members in Kabwe, Zambia.
  John Yabe; Shouta Mm Nakayama; Hokuto Nakata; Haruya Toyomaki; Yared B Yohannes; Kaampwe Muzandu; Andrew Kataba; Golden Zyambo; Masato Hiwatari; Daiju Narita; Daichi Yamada; Peter Hangoma; Nosiku Sipilanyambe Munyinda; Tiza Mufune; Yoshinori Ikenaka; Kennedy Choongo; Mayumi Ishizuka
  Chemosphere, 243, 125412, 125412, Mar. 2020, [Peer-reviewed], [International Magazine]
  English, Childhood lead (Pb) poisoning has devastating effects on neurodevelopment and causes overt clinical signs including convulsions and coma. Health effects including hypertension and various reproductive problems have been reported in adults. Historical Pb mining in Zambia's Kabwe town left a legacy of environmental pollution and childhood Pb poisoning. The current study aimed at establishing the extent of Pb poisoning and exposure differences among family members in Kabwe as well as determining populations at risk and identify children eligible for chelation therapy. Blood samples were collected in July and August 2017 from 1190 household members and Pb was measured using a portable LeadCare-II analyser. Participants included 291 younger children (3-months to 3-years-old), 271 older children (4-9-years-old), 412 mothers and 216 fathers from 13 townships with diverse levels of Pb contamination. The Blood Lead Levels (BLL) ranged from 1.65 to 162  μg/dL, with residents from Kasanda (mean 45.7  μg/dL) recording the highest BLL while Hamududu residents recorded the lowest (mean 3.3  μg/dL). Of the total number of children sampled (n = 562), 23% exceeded the 45  μg/dL, the threshold required for chelation therapy. A few children (5) exceeded the 100  μg/dL whereas none of the parents exceeded the 100  μg/dL value. Children had higher BLL than parents, with peak BLL-recorded at the age of 2-years-old. Lead exposure differences in Kabwe were attributed to distance and direction from the mine, with younger children at highest risk. Exposure levels in parents were equally alarming. For prompt diagnosis and treatment, a portable point-of-care devise such as a LeadCare-II would be preferable in Kabwe.
• Avian interspecific differences in VKOR activity and inhibition: Insights from amino acid sequence and mRNA expression ratio of VKORC1 and VKORC1L1.
  Shouta M M Nakayama; Ayuko Morita; Yoshinori Ikenaka; Yusuke K Kawai; Kensuke P Watanabe; Chihiro Ishii; Hazuki Mizukawa; Yared B Yohannes; Keisuke Saito; Yukiko Watanabe; Masaki Ito; Natsuo Ohsawa; Mayumi Ishizuka
  Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 228, 108635, 108635, Feb. 2020, [International Magazine]
  English, Worldwide use of anticoagulant rodenticides (ARs) for rodents control has frequently led to secondary poisoning of non-target animals, especially raptors. In order to suggest some factors that may help considering the mechanism of the incidents, this study focused on the avian vitamin K 2, 3-epoxide reductase (VKOR) that is the target protein of ARs. We addressed the interspecific differences in VKOR activity and inhibition related to amino acid sequence and mRNA expression of VKORC1 and VKORC1-like1 (VKORC1L1). Poultry have been considered to be more tolerant to ARs than mammals. However, VKOR activity of owls, hawks, falcon and surprisingly, canaries, was lower and inhibited by warfarin more easily than that of chickens and turkeys. The amino acid sequence of VKORC1 and VKORC1L1 implied that the value of Ki for VKOR activity to ARs could depend on the amino acid at position 140 in the TYX warfarin-binding motif in VKORC1, and other amino acid mutations in VKORC1L1. The mRNA expression ratio of VKORC1:VKORC1L1 differed between turkey (8:1) and chicken (2:3) liver. VKORC1L1 has been reported to be resistant to warfarin compared to VKORC1. Hence, both the Ki of specific VKORC1 and VKORC1L1, and the mRNA expression ratio would cause avian interspecific difference of the VKOR inhibition. Our study also suggested the high inhibition of VKOR activities in raptors and surprisingly that in canaries as well. These factors are the most likely to contribute to the high sensitivity to ARs found in raptors.
• Factors associated with lead (Pb) exposure on dogs around a Pb mining area, Kabwe, Zambia.
  Haruya Toyomaki; John Yabe; Shouta M M Nakayama; Yared B Yohannes; Kaampwe Muzandu; Allan Liazambi; Yoshinori Ikenaka; Takeshi Kuritani; Mitsuhiro Nakagawa; Mayumi Ishizuka
  Chemosphere, 247, 125884, 125884, Elsevier BV, 13 Jan. 2020, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Lead (Pb)-poisoning is a serious public health concern and dogs have been useful as a sentinel-animal for Pb exposure of humans. In the present study, the blood Pb concentrations (BLC), isotope ratios (208 Pb/206 Pb and 207 Pb/206 Pb), and biochemistry of 120 domestically owned dogs living around a Pb mining area, in Kabwe, Zambia were analyzed to determine factors associated with Pb exposure. The overall mean value of Pb in dog blood in the present study was 271.6 μg/L. The BLC in the dogs from sites near the mine were significantly higher than those in the dogs from a site 4 km from the mine (352.9 ± 205.1 μg/L versus 28.0 ± 13.9 μg/L). BLC significantly decreased with both increasing age of the dogs and distance from the mine. The Pb isotope ratios in the dog that resided near the mine showed values similar to those reported at the galena mine in Kabwe, which is considered to be the source of Pb exposure. In contrast to the high metal exposure that was determined in these dogs, the mean values of most analyzed parameters in the blood biochemical analysis were surprisingly within or close to the standard reference values. Moreover, none of the dogs showed overt signs of Pb-poisoning or other clinical symptoms. The results of analysis of Pb exposure of the dogs obtained in the present study, which are similar to the previously reported results in human in this location, suggest that dogs could be useful as a sentinel animal for Pb exposure of humans in Kabwe.
• Dichlorodiphenyltrichloroethane (DDT) levels in rat livers collected from a malaria vector control region.
  Kodai Motohira; Yoshinori Ikenaka; Yared Beyene Yohannes; Shouta M M Nakayama; Victor Wepener; Nico J Smit; Johan H J VAN Vuren; Ana Catarina Sousa; Alex Ajeh Enuneku; Emmanuel Temiotan Ogbomida; Mayumi Ishizuka
  The Journal of veterinary medical science, 81, 11, 1575, 1579, 14 Nov. 2019, [Peer-reviewed], [Domestic magazines]
  English, Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide that has been used for indoor residual spraying for the control of mosquito-borne diseases including malaria. However, due to its toxicity and environmental persistence, there are concerns about its potential deleterious effects in humans and wildlife. Therefore, the current study aimed to monitor and estimate the level of DDTs in human communities. The accumulation of DDT and its metabolites was evaluated in house rat (as sentinel) livers collected in an area where DDT was sprayed. DDTs were measured using a gas chromatography / Electron Capture Detector. The results revealed high concentrations of DDTs in the rat livers and the levels of DDTs were similar to findings reported from the same area in 2014.
• Bioaccumulation of persistent organic pollutants and their trophic transfer through the food web: Human health risks to the rural communities reliant on fish from South Africa's largest floodplain
  C.M. Volschenk; R. Gerber; M.T. Mkhonto; Y. Ikenaka; Y.B. Yohannes; S. Nakayama; M. Ishizuka; J.H.J. van Vuren; V. Wepener; N.J. Smit
  Science of The Total Environment, 685, 1116, 1126, Elsevier BV, Oct. 2019
  Scientific journal
• One year exposure to Cd- and Pb-contaminated soil causes metal accumulation and alteration of global DNA methylation in rats.
  Shouta M M Nakayama; Hokuto Nakata; Yoshinori Ikenaka; John Yabe; Balazs Oroszlany; Yared B Yohannes; Nesta Bortey-Sam; Kaampwe Muzandu; Kennedy Choongo; Takeshi Kuritani; Mitsuhiro Nakagawa; Mayumi Ishizuka
  Environmental pollution (Barking, Essex : 1987), 252, Pt B, 1267, 1276, Sep. 2019, [Peer-reviewed], [International Magazine]
  English, Metal pollution has been associated with anthropogenic activities, such as effluents and emissions from mines. Soil could be exposure route of wild rats to metals, especially in mining areas. The aim of this study was to verify whether soil exposure under environmentally relevant circumstances results in metal accumulation and epigenetic modifications. Wistar rats were divided to three groups: 1) control without soil exposure, 2) low-metal exposure group exposed to soil containing low metal levels (Pb: 75 mg/kg; Cd: 0.4), and 3) high-metal exposure group exposed to soil (Pb: 3750; Cd: 6). After 1 year of exposure, the metal levels, Pb isotopic values, and molecular indicators were measured. Rats in the high-group showed significantly greater concentrations of Pb and Cd in tissues. Higher accumulation factors (tissue/soil) of Cd than Pb were observed in the liver, kidney, brain, and lung, while the factor of Pb was higher in the tibia. The obtained results of metal accumulation ratios (lung/liver) and stable Pb isotope ratios in the tissues indicated that the respiratory exposure would account for an important share of metal absorption into the body. Genome-wide methylation status and DNA methyltransferase (Dnmt 3a/3b) mRNA expressions in testis were higher in the high-group, suggesting that exposure to soil caused metal accumulation and epigenetic alterations in rats.
• Evidence of impacts from DDT in pelican, cormorant, stork, and egret eggs from KwaZulu-Natal, South Africa.
  H Bouwman; Y B Yohannes; S M M Nakayama; K Motohira; M Ishizuka; M S Humphries; V van der Schyff; M du Preez; A Dinkelmann; Y Ikenaka
  Chemosphere, 225, 647, 658, Jun. 2019, [International Magazine]
  English, Scientific journal, DDT remains in use for malaria control in South Africa. We quantified DDTs in aquatic bird eggs from the highly biodiverse northern KwaZulu-Natal, a province of South Africa where DDT has been used for more than 80 years for malaria control. Pelican eggs had the highest ΣDDT concentration (7200 ng/g lipid mass; lm), Little Egret eggs had 6900 ΣDDT lm, African Openbill eggs had 3400 ng/g lm ΣDDT, and White-breasted Cormorant had 2400 ng/g lm. All species had non-significantly different mean concentrations of o,p'-DDT, p,p'-DDT, and ΣDDT, but with significant differences for p,p-DDE, o,p'-DDD, p,p'-DDD, %DDT, %DDD, and %lipid. The thinnest pelican eggshell (0.40 mm) had a ΣDDT concentration of 3300 ng/g lm.; the thickest shell (0.96 mm) had the lowest ΣDDT concentration at 29 ng/g lm; a 58% difference. Linear regressions of concentrations with shell thickness for the pelican eggs were significant for p,p'-DDE and p,p'-DDD, indicating risk of reproductive impairment. Compositional profiles indicate different food webs for the different species. DDT concentrations were lower than from another DDT-sprayed locality in South Africa, possible linked to differences in hydrology and rainfall. We conclude that significant ecotoxic threats associated with DDT remain in this area, and possibly threatens birds from less polluted areas. Our findings suggest continued negative human health and environmental impacts from DDT. There is an urgency to move away from DDT as quickly as possible; alternatively, to implement practices that prevent emissions of DDT to the environment while protecting human life.
• Baseline bio-accumulation concentrations and resulting oxidative stress in Synodontis zambezensis after an acute laboratory exposure to 4,4'-DDT.
  C M Volschenk; Y Ikenaka; Y B Yohannes; S M Nakayama; M Ishizuka; E Smit; J H J van Vuren; R Greenfield
  Pesticide biochemistry and physiology, 156, 44, 55, May 2019, [International Magazine]
  English, Scientific journal, The use of 1,1'-(2,2,2-Trichloro-1,1-ethanediyl)bis(4-chlorobenzene) (DDT) as a pesticide for the control of insects vectors responsible for the spread of many life threatening diseases was officially banned in 1972 by the United States Environmental Protection Agency (USEPA). It was banned throughout the world, in most developed countries, because of the toxic effects it causes in wildlife, including birds and fish. However, DDT is still used in approximately 43 African countries, including South Africa, to control the spread of malaria. The lipophilic nature of DDT and therefore its persistence in the environment makes it extremely important for laboratory based studies to be conducted in an effort to evaluate the accumulation potential and possible physiological effects of DDT in aquatic organisms under controlled conditions. The aim of this study was to establish baseline bioaccumulation concentrations within Synodontis zambezensis following an acute exposure to 4,4'-DDT. The three metabolites analysed were 4,4'-DDE, 4,4'-DDD and 4,4'-DDT. None of the 2,4'-isomers were analysed in this study since the acute exposure used a solution of 98.7% pure 4,4'-DDT (Sigma-Aldrich PESTANAL®, Analytical Standard, CAS-No 50-29-3, Batch number SZBE057XV) and not a mixture of 4,4'-DDT and 2,4'-DDT as found in technical grade DDT. Soxhlet extraction of tissue samples and liquid/liquid extraction of water samples followed by analysis through Gas-chromatography mass-spectrophotometry was completed. Mean 4,4'-DDE, 4,4'-DDD and 4,4'-DDT concentrations ranged from 15.34 ng/g to 45.34 ng/g, 28.16 ng/g to 63.25 ng/g and 28.64 ng/g to 96.21 ng/g respectively. All of the accumulated concentrations fell within environmentally relevant concentrations with no input through the food web. The accumulated concentrations of 4,4'-DDT and its three metabolites resulted in oxidative stress responses within the gills and the liver tissue of S. zambezensis. Significant differences (p ≤ .05) were observed between malondialdehyde (MDA) and reduced glutathione (GSH) within the liver and in superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) in the gills.
• Linking organochlorine exposure to biomarker response patterns in Anurans: a case study of Müller's clawed frog (Xenopus muelleri) from a tropical malaria vector control region.
  Nico J Wolmarans; Louis H Du Preez; Yared Beyene Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Nico J Smit; Victor Wepener
  Ecotoxicology (London, England), 27, 9, 1203, 1216, Nov. 2018, [International Magazine]
  English, Scientific journal, Organochlorine pesticides are highly persistent in aquatic ecosystems. Amphibians, specifically anurans, play an intricate part in the aquatic food web, and have very permeable skin which makes them prone to bioaccumulation of persistent pollutants. In this study the bioaccumulation of various legacy organochlorine pesticides (OCPs)-including dichlorodiphenyltrichloroethane (DDT), currently used for malaria vector control (MVC)-was assessed along with a set of biomarker responses in Müller's clawed frog Xenopus muelleri collected from the lower Phongolo River floodplain in South Africa. Possible relationships between bioaccumulation and biomarkers (of exposure, oxidative stress biomarkers, and cellular energy allocation) alongside their temporal changes were investigated. The OCP concentrations showed a significant increase over time for the duration of the study. The increase correlated negatively with rainfall from the region. DDT levels were well below expected effects levels with p,p-DDE being the main contributing metabolite. The results of this study indicate OCPs actively accumulate at sub-lethal levels in aquatic frogs from the study area, while showing possible relations towards some of the biochemical stress responses measured. Most notable were negative relationships indicated between p,p-DDE and acetylcholinesterase, malondialdehyde, and carbohydrates and protein energy availability. Levels of DDT were not found to be significantly higher than other legacy pesticides in the frog tissue, although evidence of newly introduced DDT in the frog tissue was found. Further investigation about sub-lethal effects of these pesticides on anurans is required to gain better insight into their full impact on animal livelihood.
• Fish consumption from urban impoundments: What are the health risks associated with DDTs and other organochlorine pesticides in fish to township residents of a major inland city.
  Wihan Pheiffer; Nico J Wolmarans; Ruan Gerber; Yared B Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Nico J Smit; Victor Wepener; Rialet Pieters
  The Science of the total environment, 628-629, 517, 527, 01 Jul. 2018, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Organochlorine pesticides (OCPs) in South Africa have for the most part been banned, except dichlorodiphenyltrichloroethane (DDT) which is still used as malaria vector control. The aim of this study was to determine OCP residues in the aquatic fauna of one of South Africa's most populated areas, Soweto. Risk to human health through OCP exposure via fish consumption was investigated. Clarias gariepinus was chosen as bioindicator because it is an apex predator that is in abundance, but is also a valued food source. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and chlordanes (CHLs) were detected in the fish tissue with the DDTs being the most prevalent at all sites. Of the three locations, Fleurhof, Orlando, and Lenasia, the latter location's fish had the highest ΣOCP load, ranging between 81 and 1190ng/gwm. The DDTs were determined to be from historic use, whereas the CHL levels indicated more recent inputs. Although the possibility of illegal use cannot be excluded completely, the presence of OCPs outside of their allowed areas of use indicate that these compounds not only stay in the aquatic systems long term, but may be of concern in areas previously not considered high risk areas. The OCP residues in C. gariepinus from the study area pose an extremely high risk to human health when consumed, and has a cancer risk as high as 1 in 10. This potential problem should be kept in consideration when developing national health and conservation strategies.
• Lead and cadmium excretion in feces and urine of children from polluted townships near a lead-zinc mine in Kabwe, Zambia.
  John Yabe; Shouta M M Nakayama; Yoshinori Ikenaka; Yared B Yohannes; Nesta Bortey-Sam; Abel Nketani Kabalo; John Ntapisha; Hazuki Mizukawa; Takashi Umemura; Mayumi Ishizuka
  Chemosphere, 202, 48, 55, Jul. 2018, [International Magazine]
  English, Scientific journal, Lead (Pb) and cadmium (Cd) are toxic metals that exist ubiquitously in the environment. Children in polluted areas are particularly vulnerable to metal exposure, where clinical signs and symptoms could be nonspecific. Absorbed metals are excreted primarily in urine and reflect exposure from all sources. We analyzed Pb and Cd concentrations in blood, feces and urine of children from polluted townships near a lead-zinc mine in Kabwe, Zambia, to determine concurrent childhood exposure to the metals. Moreover, the study determined the Pb and Cd relationships among urine, feces and blood as well as accessed the potential of urine and fecal analysis for biomonitoring of Pb and Cd exposure in children. Fecal Pb (up to 2252 mg/kg, dry weight) and urine Pb (up to 2914 μg/L) were extremely high. Concentrations of Cd in blood (Cd-B) of up to 7.7 μg/L, fecal (up to 4.49 mg/kg, dry weight) and urine (up to 18.1 μg/L) samples were elevated. metal levels were higher in younger children (0-3 years old) than older children (4-7). Positive correlations were recorded for Pb and Cd among blood, urine and fecal samples whereas negative correlations were recorded with age. These findings indicate children are exposed to both metals at their current home environment. Moreover, urine and feces could be useful for biomonitoring of metals due to their strong relationships with blood levels. There is need to conduct a clinical evaluation of the affected children to fully appreciate the health impact of these metal exposure.
• Human Health Risk from Consumption of Marine Fish Contaminated with DDT and Its Metabolites in Maputo Bay, Mozambique.
  L A Thompson; Y Ikenaka; Y B Yohannes; T Ichise; G Ito; N Bortey-Sam; J J van Vuren; V Wepener; N J Smit; W S Darwish; S M M Nakayama; H Mizukawa; M Ishizuka
  Bulletin of environmental contamination and toxicology, 100, 5, 672, 676, May 2018, [International Magazine]
  English, Scientific journal, Many countries with incidence of malaria, including those surrounding Maputo Bay, use dichloro-diphenyl-trichloroethane (DDT) to reduce mosquitoes. This study is the first to estimate the human health risk associated with consumption of marine fish from Maputo Bay contaminated with DDTs. The median for ∑DDTs was 3.8 ng/g ww (maximum 280.9 ng/g ww). The overall hazard ratio for samples was 1.5 at the 75th percentile concentration and 28.2 at the 95th percentile. These calculations show increased potential cancer risks due to contamination by DDTs, data which will help policy makers perform a risk-benefit analysis of DDT use in malaria control programs in the region.
• Investigation of mRNA expression changes associated with field exposure to DDTs in chickens from KwaZulu-Natal, South Africa.
  Lesa A Thompson; Yoshinori Ikenaka; Wageh S Darwish; Yared B Yohannes; Johan J van Vuren; Victor Wepener; Nico J Smit; Atnafu G Assefa; Ahmed Tharwat; Walaa Fathy Saad Eldin; Shouta M M Nakayama; Hazuki Mizukawa; Mayumi Ishizuka
  PloS one, 13, 10, e0204400, 2018, [International Magazine]
  English, Scientific journal, The objective of this study was to identify potential mRNA expression changes in chicken livers associated with environmental exposure to dichloro-diphenyl-trichloroethane (DDT) and its metabolites (DDTs). In particular, we focused on genes relating to the immune system and metabolism. We analyzed liver samples from free-ranging chickens in KwaZulu-Natal, South Africa, for contamination by DDTs. This area predominantly uses DDT in its malaria control program, and homes are sprayed annually with the pesticide. Genes relating to the immune system and metabolism were selected as potential genetic biomarkers that could be linked to higher contamination with DDTs. RT-qPCR analysis on 39 samples showed strong correlations between DDTs contamination and mRNA expression for the following genes: AvBD1, AvBD2, AvBD6 and AvBD7 (down-regulated), and CYP17, ELOVL2 and SQLE (up-regulated). This study shows for the first time interesting and significant correlations between genetic material collected from environmentally-exposed chickens and mRNA expression of several genes involved in immunity and metabolism. These findings show the usefulness of analysis on field samples from a region with high levels of environmental contamination in detecting potential biomarkers of exposure. In particular, we observed clear effects from DDT contamination on mRNA expression of genes involved in immune suppression, endocrine-disrupting effects, and lipid dysregulation. These results are of interest in guiding future studies to further elucidate the pathways involved in and clinical importance of toxicity associated with DDT exposure from contaminated environments, to ascertain the health risk to livestock and any subsequent risks to food security for people.
• Assessment of DDT contamination in house rat as a possible bioindicator in DDT-sprayed areas from Ethiopia and South Africa
  Yared Beyene Yohannes; Yoshinori Ikenaka; Gengo Ito; Shouta M. M. Nakayama; Hazuki Mizukawa; Victor Wepener; Nico J. Smit; Johan H. J. Van Vuren; Mayumi Ishizuka
  ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 24, 30, 23763, 23770, Oct. 2017, [Peer-reviewed]
  English, Scientific journal
• Contamination Levels and Sources of Heavy Metals and a Metalloid in Surface Soils in the Kumasi Metropolis, Ghana.
  Osei Akoto; Nesta Bortey-Sam; Yoshinori Ikenaka; Shouta M M Nakayama; Elvis Baidoo; Yared Beyene Yohannes; Mayumi Ishizuka
  Journal of health & pollution, 7, 15, 28, 39, Sep. 2017, [International Magazine]
  English, Scientific journal, Background: Environmental contamination with heavy metals and metalloids due to industrial, smelting and mining activities have become common in large and growing cities. Kumasi is one of the most industrialized cities in Ghana and experiences metal pollution due to recent and past activities. Although metals are naturally abundant in the area, their accumulation in soils could potentially lead to adverse effects on local ecosystems. Objectives: The aims of this study were to determine the distribution, enrichment, geoaccumulation and sources of metals in Kumasi soils and to estimate the contamination factor (CF) and pollution load index (PLI) of these metals in soils. Methods: Concentrations of eight heavy metals and a metalloid were determined in 112 soil samples randomly collected from 31 sampling sites in the area. In addition, 5 soil samples were collected from a pristine site (Kwame Nkrumah University of Science and Technology Botanical Gardens) for data comparison, to determine the local background values for metal concentrations and to evaluate the extent of metal pollution in the study area. Results: Heavy metals such as zinc (Zn), lead (Pb), cadmium (Cd) and chromium (Cr) were enriched in 65, 32, 58 and 93% of the sampling sites, respectively, and geo-accumulation indexes for Cr, Zn, Cd, mercury (Hg) and Pb showed moderate to extreme contamination in 100, 97, 77, 65 and 45% of the sampling sites, respectively. Principal component and cluster analyses revealed that industrial activities including mining were the major sources of metals in Kumasi soils with high metal input in the community of Suame. Distribution maps revealed hotspots of Cd, nickel (Ni), arsenic (As), cobalt (Co), copper (Cu) and Pb in Suame. The highest CFs for Cu, Cd, Ni, As, Co and Pb highlighted anthropogenic inputs in Suame, while Hg was highest in Mbrom, Zn in Suntreso, and Cr in Aboabo. Conclusions: The PLI of metals revealed Suame as the most polluted study site, while Anomangye and Bomso were the least polluted.
• Contamination status and accumulation characteristics of heavy metals and arsenic in five seabird species from the central Bering Sea
  Chihiro Ishii; Yoshinori Ikenaka; Shouta M. M. Nakayama; Hazuki Mizukawa; Yared Beyene Yohannes; Yutaka Watanuki; Masaaki Fukuwaka; Mayumi Ishizuka
  JOURNAL OF VETERINARY MEDICAL SCIENCE, 79, 4, 807, 814, Apr. 2017, [Peer-reviewed], [Domestic magazines]
  English, Scientific journal
• Trace Element Contamination in Tissues of Four Bird Species from the Rift Valley Region, Ethiopia
  Yared Beyene Yohannes; Yoshinori Ikenaka; Shouta M. M. Nakayama; Hazuki Mizukawa; Mayumi Ishizuka
  BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY, 98, 2, 172, 177, Feb. 2017, [Peer-reviewed]
  English, Scientific journal
• Monitoring Lead (Pb) Pollution and Identifying Pb Pollution Sources in Japan Using Stable Pb Isotope Analysis with Kidneys of Wild Rats.
  Hokuto Nakata; Shouta M M Nakayama; Balazs Oroszlany; Yoshinori Ikenaka; Hazuki Mizukawa; Kazuyuki Tanaka; Tsunehito Harunari; Tsutomu Tanikawa; Wageh Sobhy Darwish; Yared B Yohannes; Aksorn Saengtienchai; Mayumi Ishizuka
  International journal of environmental research and public health, 14, 1, 10 Jan. 2017, [Peer-reviewed], [International Magazine]
  English
• Concentrations and human health risk assessment of DDT and its metabolites in free-range and commercial chicken products from KwaZulu-Natal, South Africa
  L. A. Thompson; Y. Ikenaka; Y. B. Yohannes; J. J. van Vuren; V. Wepener; N. J. Smit; W. S. Darwish; S. M. M. Nakayama; H. Mizukawa; M. Ishizuka
  FOOD ADDITIVES AND CONTAMINANTS PART A-CHEMISTRY ANALYSIS CONTROL EXPOSURE & RISK ASSESSMENT, 34, 11, 1959, 1969, 2017, [Peer-reviewed]
  English, Scientific journal
• DDTs and other organochlorine pesticides in tissues of four bird species from the Rift Valley region, Ethiopia
  Yared Beyene Yohannes; Yoshinori Ikenaka; Shouta M. M. Nakayama; Hazuki Mizukawa; Mayumi Ishizuka
  SCIENCE OF THE TOTAL ENVIRONMENT, 574, 1389, 1395, Jan. 2017, [Peer-reviewed]
  English, Scientific journal
• Bioaccumulation and human health risk assessment of DDT and other organochlorine pesticides in an apex aquatic predator from a premier conservation area
  Ruan Gerber; Nico J. Smit; Johan H. J. Van Vuren; Shouta M. M. Nakayama; Yared B. Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Victor Wepener
  SCIENCE OF THE TOTAL ENVIRONMENT, 550, 522, 533, Apr. 2016, [Peer-reviewed]
  English, Scientific journal
• Distribution and health risk assessment of organochlorine pesticides (OCPs) residue in edible cattle tissues from northeastern part of Egypt: High accumulation level of OCPs in tongue
  Abdallah Fikry A. Mahmoud; Yoshinori Ikenaka; Yared B. Yohannes; Wageh S. Darwish; Elsaid A. Eldaly; Alaa Eldin M. A. Morshdy; Shouta M. M. Nakayama; Hazuki Mizukawa; Mayumi Ishizuka
  CHEMOSPHERE, 144, 1365, 1371, Feb. 2016, [Peer-reviewed]
  English, Scientific journal
• Application of a Sediment Quality Index for the assessment and monitoring of metals and organochlorines in a premier conservation area
  Ruan Gerber; Nico J. Smit; Johan H. J. van Vuren; Shouta M. M. Nakayama; Yared B. Yohannes; Yoshinori Ikenaka; Mayumi Ishizuka; Victor Wepener
  ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 22, 24, 19971, 19989, Dec. 2015, [Peer-reviewed]
  English, Scientific journal
• Metal extent in blood of livestock from Dandora dumping site, Kenya: Source identification of Pb exposure by stable isotope analysis.
  Hokuto Nakata; Shouta M M Nakayama; Yoshinori Ikenaka; Hazuki Mizukawa; Chihiro Ishii; Yared B Yohannes; Satoru Konnai; Wageh Sobhy Darwish; Mayumi Ishizuka
  Environmental pollution (Barking, Essex : 1987), 205, 8, 15, Oct. 2015, [Peer-reviewed], [International Magazine]
  English
• Levels, potential sources and human health risk of polycyclic aromatic hydrocarbons (PAHs) in particulate matter (PM10) in Kumasi, Ghana
  Nesta Bortey-Sam; Yoshinori Ikenaka; Osei Akoto; Shouta M. M. Nakayama; Yared Beyene Yohannes; Elvis Baidoo; Hazuki Mizukawa; Mayumi Ishizuka
  ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 22, 13, 9658, 9667, Jul. 2015, [Peer-reviewed]
  English, Scientific journal
• Human health risks from metals and metalloid via consumption of food animals near gold mines in Tarkwa, Ghana: Estimation of the daily intakes and target hazard quotients (THQs)
  Nesta Bortey-Sam; Shouta M. M. Nakayama; Yoshinori Ikenaka; Osei Akoto; Elvis Baidoo; Yared Beyene Yohannes; Hazuki Mizukawa; Mayumi Ishizuka
  ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, 111, 160, 167, Jan. 2015, [Peer-reviewed]
  English, Scientific journal
• Lead poisoning in children from townships in the vicinity of a lead-zinc mine in Kabwe, Zambia
  John Yabe; Shouta M. M. Nakayama; Yoshinori Ikenaka; Yared B. Yohannes; Nesta Bortey-Sam; Balazs Oroszlany; Kaampwe Muzandu; Kennedy Choongo; Abel Nketani Kabalo; John Ntapisha; Aaron Mweene; Takashi Umemura; Mayumi Ishizuka
  CHEMOSPHERE, 119, 941, 947, Jan. 2015, [Peer-reviewed]
  English, Scientific journal
• Occurrence, distribution, sources and toxic potential of polycyclic aromatic hydrocarbons (PAHs) in surface soils from the Kumasi Metropolis, Ghana
  Nesta Bortey-Sam; Yoshinori Ikenaka; Shouta M. M. Nakayama; Osei Akoto; Yared Beyene Yohannes; Elvis Baidoo; Hazuki Mizukawa; Mayumi Ishizuka
  SCIENCE OF THE TOTAL ENVIRONMENT, 496, 471, 478, Oct. 2014, [Peer-reviewed], [International Magazine]
  English, Scientific journal
• Organochlorine pesticides in bird species and their prey (fish) from the Ethiopian Rift Valley region, Ethiopia
  Yared Beyene Yohannes; Yoshinori Ikenaka; Shouta M. M. Nakayama; Mayumi Ishizuka
  ENVIRONMENTAL POLLUTION, 192, 121, 128, Sep. 2014, [Peer-reviewed]
  English, Scientific journal
• Concentrations and human health risk assessment of organochlorine pesticides in edible fish species from a Rift Valley lake-Lake Ziway, Ethiopia
  Yared B. Yohannes; Yoshinori Ikenaka; Aksorn Saengtienchai; Kensuke P. Watanabe; Shouta M. M. Nakayam; Mayumi Ishizuka
  ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, 106, 95, 101, Aug. 2014, [Peer-reviewed]
  English, Scientific journal
• Contamination status and accumulation characteristics of metals and a metalloid in birds on Teuri Island, Hokkaido, Japan
  Chihiro Ishii; Yoshinori Ikenaka; Shouta M. M. Nakayama; Yuya Suzuki; Yutaka Watanuki; Yuji Watanabe; Yared Beyene Yohannes; Hazuki Mizukawa; Mayumi Ishizuka
  JAPANESE JOURNAL OF VETERINARY RESEARCH, 62, 3, 143, 149, Aug. 2014, [Peer-reviewed], [Domestic magazines]
  English, Scientific journal
• Occurrence, distribution, and ecological risk assessment of DDTs and heavy metals in surface sediments from Lake Awassa-Ethiopian Rift Valley Lake
  Yared Beyene Yohannes; Yoshinori Ikenaka; Aksorn Saengtienchai; Kensuke P. Watanabe; Shouta M. M. Nakayama; Mayumi Ishizuka
  ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 20, 12, 8663, 8671, Dec. 2013, [Peer-reviewed]
  English, Scientific journal
• Organochlorine pesticides and heavy metals in fish from Lake Awassa, Ethiopia: Insights from stable isotope analysis
  Yared Beyene Yohannes; Yoshinori Ikenaka; Shouta M. M. Nakayama; Aksorn Saengtienchai; Kensuke Watanabe; Mayumi Ishizuka
  CHEMOSPHERE, 91, 6, 857, 863, May 2013, [Peer-reviewed]
  English, Scientific journal

• Intergenerational sex-specific transcriptomic alterations in gonads of mice after parental lead exposure (vol 140, 109154, 2026)
  Nelly Banda; Kanami Watanabe; John Yabe; Rio Doya; Kaampwe Muzandu; Yared Beyene Yohannes; Andrew Kataba; Yoshinori Ikenaka; Mayumi Ishizuka; Shouta M. M. Nakayama, REPRODUCTIVE TOXICOLOGY, 141, Apr. 2026
  English, Others
• Analysis of changing metabolomes in the brains ofmice exposed to neonicotinoids using LC/Q-TOF/MS
  小池智也; 江口哲史; 野見山桂; 平野哲史; NIMAKO Collins; YOHANNES Yared Beyene; 中山翔太; 石塚真由美; 池中良徳, 環境化学討論会要旨集(CD-ROM), 33rd, 2025
• 鉛中毒マウスの短期作業記憶低下および血中ステロイドの分析
  村上昂暉; 中山翔太; 一瀬貴大; 中田北斗; YARED B. Yohannes; YARED B. Yohannes; ANDREW Kataba; ANDREW Kataba; 平井杏梨; 池中良徳; 石塚真由美, 日本獣医学会学術集会講演要旨集, 164th (CD-ROM), 2021
• マラリアベクターコントロールにおけるDDTの使用実態とリスク評価
  池中良徳; THOMPSON Lesa; DARWISH Wageh; YOHANNES Yared; VAN VUREN Johan; SMIT Nico; WEPENER Victor; 中山翔太; 水川葉月; 石塚真由美, 環境化学討論会要旨集(CD-ROM), 27th, 2018
• Heavy metal pollution in Japanese seabirds
  Chihiro Ishii; Yoshinori Ikenaka; Shouta M.M. Nakayama; Yuya Suzuki; Yutaka Watanuki; Yuji Watanabe; Masa aki Fukuwaka; Yared B. Yohannes; Yusuke K. Kawai; Mayumi Ishizuka, Japanese Journal of Veterinary Research, 61, SUPPL., 2013
  Report scientific journal