UV-A Coexposure Enhances the Toxicity of AromaticHydrocarbons, Munitions, and Metals to Photobacterium phosphoreum

Johnson et al. (1993) showed that coexposure to UV-A between 300-400 nm enhanced the toxicity of nitrotoluenes to Phoiobacterium phosphoreum, a marine bioluminescent bacteria used in the Microtox test (Microbics Inc.). This paper reports that UV-A photoenhanced the toxicity of polynuclear aromatic hydrocarbons, other types of organic compounds, and some transition metals to P. phosphoreum. Coexposure to 400 μw/cm2 for 15 min increased the toxicity of psoralen, α-terthienyl, anthracene, acridine, fluoranthene,TNT, Cu2+, As3+, Ni2, and Cd2+. Phenanthrene was photoenhanced after 30 min coexposure at 400 μw/cm2+, and Mn2+ at 800 μw/cm2 aftef 15 min. Naphthalene was not enhanced at 800 μw/cm2 for 30 min

Benchmark Dose for Dioxin Based on Gestational Diabetes Mellitus Using Coexposure Statistical Methods and an Optimized Physiologically Based Toxicokinetic Model

Dioxins are ubiquitous endocrine-disrupting substances,but determining the effects and benchmark doses in situations of coexposure is highly challenging.The objective of this study was to assess the relationship between dioxin andgestational diabetes mellitus(GDM),calculate the benchmark dose(BMD)of dioxin in coexposure scenarios,and derive a daily exposure threshold using an optimized physiologically based toxicokinetic(PBTK)model.Based on a nested casecontrol study including 77 cases with GDM and 154 controls,serum levels of 29 dioxin-like compounds(DLCs)along with 10 perfluoroalkyl acids(PFAAs),seven polybrominated diphenyl ethers(PBDEs),and five non-dioxin-like polychlorinated biphenyls(ndl-PCBs)were measured at 9−16 weeks of gestation.Bayesian machine kernel regression(BKMR)was employed to identify significant chemicals,and probit and logistic models were used to calculate BMD adjusted for significant chemicals.A physiologically based toxicokinetic(PBTK)model was optimized using polyfluorinated dibenzo-p-dioxins and dibenzofurans(PFDD/Fs)data by the Bayesian−Monte Carlo Markov chain method and was used to determine the daily dietary exposure threshold.The median serum level of total dioxin toxic equivalent(TEQ)was 7.72 pg TEQ/g fat.Logistic regression analysis revealed that individuals in the fifth quantile of total TEQ level had significantly higher odds of developing GDM compared to those in the first quantile(OR,8.87;95%CI 3.19,27.58).The BKMR analysis identified dioxin TEQ and BDE-153 as the compounds with the greatest influence.The binary logistic and probit models showed that the BMD10(benchmark dose corresponding to a 10%extra risk)and BMDL_(10)(lower bound on the BMD_(10))were 3.71 and 3.46 pg TEQ/g fat,respectively,when accounting for coexposure to BDE-153 up to the 80%level.Using the optimized PBTK model and modifying factor,it was estimated that daily exposure should be below 4.34 pg TEQ kg^(−1)bw week^(−1)in order to not reach a harmful serum concentration for GDM.Further studies should utilize coexposure statistical methods and physiologically based pharmacokinetic(PBTK)models in reference dose calculation.

Effects of Selected Metal Oxide Nanoparticles on Multiple Biomarkers in Carassius auratus

Objective To study the biological effects of nanoscale copper oxide （nCuO）, zinc oxide （nZnO）, cerium dioxide （nCeO2） and their mixtures on Carassius auratus. Methods Juvenile fish （Carossius auratus） were exposed to aqueous suspensions of nCuO, nZnO, and nCeO2 （alone and in mixtures） at concentrations of 20, 40, 80, 3.60, and 320 mg/L. The biomarkers-acetylcholinesterase （ACHE） in brain, sodium/potassium-activated ATPase （Na~/K＊-ATPase） in gill, and superoxide dismutase （SOD） and catalase （CAT） in liver-were determined after 4 days of exposure. Integrated biomarker response （IBR） was calculated by combining multiple biomarkers into a single value. Results AChE and SOD activities were significantly inhibited by all test metal oxide nanoparticles （NPs） at high concentrations （__.160 rag/L） with the exception of nCeO2. Na~/K＋-ATPase induction exhibited bell-shaped concentration-response curves. CAT activity was significantly inhibited at concentrations equal to or higher than 160 mg/L. The order of IBR values was nCeO2 = nZnO/nCeO2= nCuO/nCeO2 〈 nCuO/nZnO/nCeO2 〈 nZnO 〈 nCuO 〈 nCuO/nZnO. The joint effect seemed to be synergistic for nCuO/nZnO mixtures, additive for the ternary mixture and less than additive or antagonistic for the binary mixtures containing nCe02. Conclusion Concentration-dependent changes of enzymatic activities （ACHE, Na~/K＊-ATPase, SOD, and CAT） were observed in fish exposed to nanoscale metal oxides. IBR analysis allowed good discrimination between the different exposures and might be a useful tool for the quantification of integrated negative effects induced by NPs toward fish.

Association of Multiple Urinary Phthalates Metabolites with Diabetes Risk in Elderly Population

As a common environmental endocrine disruptor,phthalate exposure could affect the diabetes risk.However,it remains unclear whether phthalate exposure in the elderly population alters diabetes risk.We conducted a cross-sectional survey to explore the effect of urinary phthalate metabolites on diabetes in the elderly.We conducted a health survey of 200 elderly in northeastern China and measured urinary concentrations of 64 phthalate metabolites.We next evaluated the association between major phthalates and phthalate mixtures and diabetes in the elderly.The least absolute shrinkage and selection operator(LASSO)regression screened for mono(3-carboxypropyl)phthalate(MCPP),monoethyl phthalate(MEP),and mono(2-ethyl-5-hydroxyhexyl)phthalate(MEHHP)as important predictors for diabetes.Weighted quantile sum(WQS)regression and Bayesian Kernel Machine regression(BKMR)models consistently found MEHHP(Weights=51.9%,PIP=0.97)to have the greatest effect on diabetes risk in the elderly.Furthermore,MEHHP was associated with an increased risk of diabetes in the multipollutant logistic regression model(OR=2.148,95%CI:1.255 to 3.677).The overall effect of coexposure to MCPP,MEHHP,and MEP on the risk of diabetes in elderly population was significant and positive.In summary,we found that increased urinary MEHHP levels could increase the risk of diabetes in the elderly population.Co-exposure to MCPP,MEHHP and MEP may increase the risk of diabetes.