Exposure to bisphenol S alters the expression of microRNA in male zebrafish.

Bisphenol S (BPS), an alternative compound of bisphenol A, has been found to affect reproduction, development, and immune system. Although microRNAs (miRNAs) play an important role in many metabolic activities, whether and how they are involved in the process of BPS-induced toxicity is unknown. In the present study, BPS-induced changes in miRNAs and target gene expression in male zebrafish gonad, and the potential mechanism was investigated. Male zebrafish were exposed to 0, 5, and 50µg/L BPS for 21 d. miRNA was isolated from the gonad pool and the expression profiles of 255 known zebrafish miRNAs were analyzed using microarrays. Quantitative real-time polymerase chain reaction was used to validate the expression of several miRNAs in the microarray data. The GO term analysis revealed that miRNAs significantly affected by BPS exposure were involved in hematopoiesis, lymphoid organ development, and immune system development. Among 14 miRNAs that were significantly regulated after exposure to 5 and 50µg/L BPS, six targeted cyp19a1b gene, suggesting the role of BPS-induced toxicity via the interference with the aromatization process. Our findings provide novel insight into the epigenetic regulatory mechanisms of BPS-induced toxicity in male zebrafish, and identification of novel miRNA biomarkers for exposure to BPS.

Effects of chronic exposure to cefadroxil and cefradine on Daphnia magna and Oryzias latipes.

Cefadroxil and cefradine have frequently been detected in surface waters, however toxicological studies in aquatic organisms have mostly been limited to acute lethal effects. In the present study, endocrine disruption caused by cefadroxil and cefradine, and its underlying mechanism were investigated by chronic exposure of Daphnia magna (21 d) and Oryzias latipes (120 d). In medaka fish, the effects on growth, mortality, and reproduction, as well as on the levels of hormones and genes related to the hypothalamic-pituitary-gonad (HPG) axis, were investigated after 120 d exposure. In D. magna, the chronic effects on growth were observed at the highest concentration of 83.0 mg L-1 cefadroxil and 80.8 mg L-1 cefradine. The growth of juvenile fish was significantly impaired by exposure to cefradine. Following exposure to cefadroxil and cefradine for 120 d, sex-dependent changes in E2 hormones were observed and their levels were supported by the regulation of genes along the HPG axis. We found that chronic exposure to cefadroxil and cefradine impaired growth and reproduction in a freshwater invertebrate and fish, and altered the levels of sex hormones and genes associated with the HPG axis in fish.

Urinary levels of phthalate metabolites and associations with demographic characteristics in Korean adults.

The objective of this study is to assess human exposure to phthalates and its associations with demographic characteristics of the subjects in the Korean National Human Biomonitoring Survey. The subjects aged between 18 and 69 were selected through nationwide stratified sampling. A total of 1874 urine samples were collected and stored at -20 °C until measurement for ten selected metabolites of phthalates (MnBP, MiBP, MBzP, MCHP, MnOP, MEHP, MEOHP, MEHHP, MiNP, and MiDP) using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The difference in the level of urinary phthalate metabolites by the characteristics of the subjects was tested for statistical significance using SAS Surveyreg procedure. The coefficients and standard errors from multiple linear regressions were exponentiated to estimate the adjusted proportional change (APC) and 95% CIs compared with a referent level. The proportion of data above LOQ was less than 20% for MCHP, MnOP, MiNP, and MiDP. Geometric means of creatinine-adjusted concentrations (unit: µg/g creatinine) of six other phthalate metabolites among Korean adults were 41.7 (95% CI 39.6-43.9) for MnBP, 17.1 (95% CI 16.1-18.1) for MiBP, 15.7 (95% CI 14.4-17.1) for MBzP, 8.65 (95% CI 8.10-9.22) for MEHP, 17.5 (95% CI 16.8-18.3) for MEOHP, and 38.1 (95% CI 36.2-40.2) for MEHHP. Urinary level of phthalates tended to be higher among subjects with older age, females, and those with vigorous daily physical activity and tended to be lower among drinkers and those with higher income. Our results suggest that the level of phthalate exposure is significant among Korean adults and thus warrants further studies to identify major source and route of exposure to phthalates.

Thyroid endocrine disruption in male zebrafish following exposure to binary mixture of bisphenol AF and sulfamethoxazole.

Thyroid endocrine disruption by bisphenol AF (BPAF) alone or in combination with sulfamethoxazole (SMX) exposure was evaluated in adult male zebrafish. Changes in thyroid gene transcription were examined using microarrays and were linked to effects on thyroxine hormone production and transcription of genes related to the hypothalamic-pituitary-thyroid axis. BPAF alone or in combination with SMX affected genes related to thyroid hormone production and receptor activity, thyroid gland development, and deiodinase activity. Increases in thyroxine levels, and gene transcription were more pronounced in the BPAF and SMX mixture group than in the BPAF group. Significant down-regulation of trh and tshß genes in the brain suggested a negative feedback response resulting in increased thyroxine levels. The present study indicated that BPAF exposure alone alters transcription of genes associated with the thyroid endocrine system, and combination with SMX could increase the endocrine disrupting effect of BPAF.

Characterization of Total and Size-Fractionated Manganese Exposure by Work Area in a Shipbuilding Yard.

BACKGROUND: Shipbuilding involves intensive welding activities, and welders are exposed to a variety of metal fumes, including manganese, that may be associated with neurological impairments. This study aimed to characterize total and size-fractionated manganese exposure resulting from welding operations in shipbuilding work areas. METHODS: In this study, we characterized manganese-containing particulates with an emphasis on total mass (n = 86, closed-face 37-mm cassette samplers) and particle size-selective mass concentrations (n = 86, 8-stage cascade impactor samplers), particle size distributions, and a comparison of exposure levels determined using personal cassette and impactor samplers. RESULTS: Our results suggest that 67.4% of all samples were above the current American Conference of Governmental Industrial Hygienists manganese threshold limit value of 100 µg/m(3) as inhalable mass. Furthermore, most of the particles containing manganese in the welding process were of the size of respirable particulates, and 90.7% of all samples exceeded the American Conference of Governmental Industrial Hygienists threshold limit value of 20 µg/m(3) for respirable manganese. CONCLUSION: The concentrations measured with the two sampler types (cassette: total mass; impactor: inhalable mass) were significantly correlated (r = 0.964, p < 0.001), but the total concentration obtained using cassette samplers was lower than the inhalable concentration of impactor samplers.

Major benzophenone concentrations and influence of food consumption among the general population in Korea, and the association with oxidative stress biomarker.

Benzophenones (BPs) have been used as sunscreen agents and as ultraviolet stabilizers in plastic surface coatings for food packaging. However, few studies have been performed to examine the level of human exposure to BPs and the potential sources of such exposure. We evaluated the exposure levels to six major BPs (BP-1, BP-2, BP-3, BP-4, BP-8, and 4-hydroxybenzophenone (4-OH-BP)) among the adult population in two cities in Korea, and investigated the potential dietary sources of the BPs. Urinary levels of malondialdehyde (MDA) as an oxidative stress biomarker as well as their association with the levels of BPs were also analyzed. Among the six BPs analyzed, 4-OH-BP, BP-1, BP-3, and BP-4 were detected in 77%, 49%, 27%, and 21% of the population, respectively. BP concentrations were relatively higher in younger (people in their 20s and 30s) cosmetic users and leaner women. Even after the adjustment of age, body mass index, and cosmetic use, the consumption of frozen storage food, instant noodles, and instant coffee was significantly correlated with urinary BPs, and these associations were sex-dependent. No significant correlation was observed between the levels of BPs and levels of MDA. The results of the present study will be useful for developing plans of public health management of BPs.

Effects of Barium Chloride Exposure on Hormones and Genes of the Hypothalamic-Pituitary-Gonad Axis, and Reproduction of Zebrafish (Danio rerio).

Adult zebrafish pairs were exposed to sub-lethal concentrations of BaCl2 for 21 days, and the effects on reproduction, sex steroid hormones, and transcription of the genes belonging to the hypothalamic-pituitary-gonad (HPG) axis were investigated. The adverse effects on performances of F1 generation were further examined with or without subsequent exposure to BaCl2. Egg production was significantly decreased, and parental exposure to BaCl2 resulted in lesser rates of hatching. In males, exposure to BaCl2 resulted in greater concentrations of E2 along with greater mRNA expression of cyp19a. The results demonstrated that BaCl2 could modulate gene transcriptions and hormone production of the HPG axis in a sex-dependent way, which could cause adverse effects on reproduction and the development of offspring.

Risk assessment of chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin in aquatic environment: are the current environmental concentrations safe?

To understand potential risks of major pharmaceutical residues in waters, we evaluated ecotoxicities of five major veterinary pharmaceuticals, i.e., chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin, which have been frequently detected in freshwater environment worldwide. We conducted acute and chronic toxicity tests using two freshwater invertebrates (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). In general, D. magna exhibited greater sensitivity than M. macrocopa, and chronic reproduction was the most sensitive endpoints for both organisms. The population growth rate was adversely influenced by exposure to chlortetracycline, sulfamethazine, or sulfathiazole in water fleas, but reduction in population size was not expected. In O. latipes, the tested pharmaceuticals affected several reproduction related endpoints including time to hatch and growth. Based on the toxicity values from the present study and literature, algae appeared to be the most sensitive organism, followed by Daphnia and fish. Hazard quotients derived from measured environmental concentrations (MECs) and predicted no effect concentrations (PNECs) for erythromycin and oxytetracycline exceeded unity, suggesting that potential ecological effects at highly contaminated sites cannot be ruled out. Long-term consequences of veterinary pharmaceutical contamination in the environment deserve further investigation.

Determination of Phthalate Metabolites in Human Serum and Urine as Biomarkers for Phthalate Exposure Using Column-Switching LC-MS/MS.

OBJECTIVES: Although phthalates like dibutyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) are commonly used as plasticizers and their metabolites are especially suspected of reproductive toxicity, little is known about occupational exposure to those phthalates. The aim of this study was to assess the utility of measuring the metabolite concentrations of DBP and DEHP in serum and urine samples as an indicator of occupational exposure to those phthalates. METHODS: Phthalate metabolites were analyzed by using column-switching high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). RESULTS: We detected phthalate metabolites in serum and urine matrices at approximately 10-fold lower than the limit of detection of those metabolites in the same matrix by LC-MS/MS without column switching, which was sufficient to evaluate concentrations of phthalate metabolites for industrial workers and the general population. CONCLUSION: The accuracy and precision of the analytical method indicate that urinary metabolite determination can be a more acceptable biomarker for studying phthalate exposure and adverse health outcomes.

Extensive changes to occupational exposure limits in Korea.

Occupational exposure limits (OELs) are used as an important tool to protect workers from adverse chemical exposures and its detrimental effects on their health. The Ministry of Labor (MOL) can establish and publish OELs based on the Industrial Safety and Health Act in Korea. The first set of OELs was announced by the MOL in 1986. At that time, it was identical to the Threshold Limit Values of the American Conference of Governmental Industrial Hygienists. Until 2006, none the first OELs except for those of three chemicals (asbestos, benzene, and 2-bromopropane) were updated during the last twenty years. The Hazardous Agents Review Committee established under the MOL selected 126 chemicals from 698 chemicals covered by OELs using several criteria. From 2005 to 2006, the MOL provided research funds for academic institutions and toxicological laboratories to gather the evidence documenting the need to revise the outdated OELs. Finally, the MOL notified the revised OELs for 126 chemicals from 2007 to 2008. The revised OELs of 58 substances from among these chemicals were lowered to equal or less than half the value of the original OELs. This is the most substantial change in the history of OEL revisions in Korea.

Implication of global environmental changes on chemical toxicity-effect of water temperature, pH, and ultraviolet B irradiation on acute toxicity of several pharmaceuticals in Daphnia magna.

Global environmental change poses emerging environmental health challenges throughout the world. One of such threats could be found in chemical safety in aquatic ecosystem. In the present study, we evaluated the effect of several environmental factors, such as water pH, temperature and ultraviolet light on the toxicity of pharmaceutical compounds in water, using freshwater invertebrate Daphnia magna. Seven pharmaceuticals including ibuprofen, acetaminophen, lincomycin, ciprofloxacin, enrofloxacin, chlortetracycline and sulfathiazole were chosen as test compounds based on their frequent detection in water. The experimental conditions of environmental parameters were selected within the ranges that could be encountered in temperate environment, i.e., water temperature (15, 21, and 25 degrees C), pH (7.4, 8.3, and 9.2), and UV-B light intensity (continuous irradiation of 15.0 microW/cm(2)). For acetaminophen, enrofloxacin and sulfathiazole, decrease in water pH generally led to increase of acute lethal toxicity, which could be explained by the unionized fraction of pharmaceuticals. Increase of water temperature enhanced the acute toxicity of the acetaminophen, enrofloxacin and chlortetracycline, potentially due to alteration in toxicokinetics of chemicals as well as impact on physiological mechanisms of the test organism. The presence of UV-B light significantly increased the toxicity of sulfathiazole, which could be explained by photo-modification of this chemical that lead to oxidative stress. Under the UV light, however, acute toxicity of enrofloxacin decreased, which might be due to photo-degradation. Since changing environmental conditions could affect exposure and concentration-response profile of environmental contaminants, such conditions should be identified and evaluated in order to better manage ecosystem health under changing global environment.

Aquatic toxicity of acetaminophen, carbamazepine, cimetidine, diltiazem and six major sulfonamides, and their potential ecological risks in Korea.

Pharmaceuticals are manufactured and used for specific biological functions in veterinary and human medicine. Their detection in the environment and their bioactivity have resulted in concern for potential adverse effects on non-target species. Notwithstanding recent attention for their occurrence in the environment, there are significant research gaps for existing pharmaceuticals with regard to their potential ecological consequences. In this study, the four most abundantly used pharmaceuticals in Korea, namely acetaminophen, carbamazepine, cimetidine, and diltiazem, and six sulfonamide related antibiotics, including sulfamethoxazole, sulfachlorpyridazine, sulfathiazole, sulfamethazine, sulfadimethoxine, and trimethoprim were examined for their acute aquatic toxicity employing a marine bacterium (Vibrio fischeri), a freshwater invertebrate (Daphnia magna), and the Japanese medaka fish (Oryzias latipes). In general, Daphnia was the most susceptible among the test organisms. The most acutely toxic among the chemicals tested in this study was diltiazem, with a median lethal concentration of 8.2 mg/L for D. magna. The resulting acute toxicity of these pharmaceuticals was reasonably predicted by physicochemical descriptors such as pH-dependent distribution coefficient and EHOMO-ELUMO gap. Predicted environmental concentrations (PECs) derived for the test pharmaceuticals in Korea ranged between 0.14 and 16.5 microg/L. Hazard quotients derived from PECs and predicted no effect concentrations (PNECs) for sulfamethoxazole and acetaminophen were 6.3 and 1.8, respectively, suggesting potential environmental concerns and a need for further investigation.

Aquatic toxicity of four alkylphenols (3-tert-butylphenol, 2-isopropylphenol, 3-isopropylphenol, and 4-isopropylphenol) and their binary mixtures to microbes, invertebrates, and fish.

The acute and chronic toxicity of four simple alkylphenols with butyl and propyl substitutions was evaluated with aquatic microbes, invertebrates, and fish. These alkylphenols-3-tert-butylphenol, 2-isopropylphenol, 3-isopropylphenol, and 4-isopropylphenol-have been detected in various environmental media, but their impact on aquatic fauna has seldom been evaluated. Relative susceptibility to each phenolic varied by test species. The marine bacterium Vibrio fischeri was the most susceptible to the alkylphenols, up to 3 orders of magnitude more sensitive than species of higher trophic levels. For 4-isopropylphenol, the 5-min Microtox EC(50) value was 0.01 mg/L, whereas the EC(50) for Ceriodaphnia after a 48-h exposure was 10.1 mg/L. Notable differences in sensitivity to the alkylphenols was also observed with the Microtox assay: 4-isopropylphenol was > 200 times more toxic to V. fischeri than was 2-isopropylphenol (EC(50) = 2.72 mg/L). For V. fischeri, the mixture toxicity of the alkylphenols was additive in nature and was predicted by a concentration addition model. The energy of the lowest unoccupied molecular orbital (ELUMO) explained the observed toxicity of the individual alkylphenols to V. fischeri (r(2) = 0.92, p < 0.05). These results suggest that the mode of action of polar narcotic alkylphenols to V. fischeri is different than that of other test organisms, possibly because of the differences in the cell structure of the prokaryotic V. fischeri.

Reduction of aflatoxins by Korean soybean paste and its effect on cytotoxicity and reproductive toxicity--Part 3. Inhibitory effects of Korean soybean paste (doen-jang) on aflatoxin toxicity in laying hens and aflatoxin accumulation in their eggs.

This study was conducted to determine the effects of Korean soybean paste (doen-jang [dwen-jahng]) (at concentrations of 0.5, 1, and 5%) on the toxicity of 500 ppb of aflatoxin in the diets of 60 laying hens (Isa Brown) divided into five groups and treated from week 15 to week 67. The aflatoxin-treated hens exhibited many deleterious effects, including reduced body weight; increased relative organ weights; decreased egg production; aflatoxin accumulation in eggs; decreased serum calcium, phosphorus, and alanino amonotransferase (ALT) levels; increased serum gammaglutamil transferase and lactic dehydrogenase levels; and, most significantly, severely altered cell foci and sinusoid dilatation in the liver, relative to control hens. The feeding of 1% soybean paste to hens reduced the adverse effects of aflatoxin on body weight, relative organ weights, egg production, and aflatoxin accumulation in eggs and improved serum calcium and ALT levels and the histopathological lesions of the liver. The feeding of 5% soybean paste to hens resulted in higher levels of the same types of improvements, especially with regard to the histopathological findings for the liver. On the basis of these results, it was suggested that a diet including 5% (and in some cases only 1%) Korean soybean paste protected laying hens and their eggs from the major deleterious effects of 500 microg of aflatoxin per kg of diet and from aflatoxin accumulation. These results indicate that dietary supplementation with Korean soybean paste reduces aflatoxin toxicity in laying hens that ultimately produce human foods such as eggs and poultry.