Method to assess component contribution to toxicity of complex mixtures: Assessment of puberty acquisition in rats exposed to disinfection byproducts

A method based on regression modeling was developed to discern the contribution of component chemicals to the toxicity of highly complex, environmentally realistic mixtures of disinfection byproducts(DBPs). Chemical disinfection of drinking water forms DBP mixtures.Because of concerns about possible reproductive and developmental toxicity, a whole mixture(WM) of DBPs produced by chlorination of a water concentrate was administered as drinking water to Sprague–Dawley(S–D) rats in a multigenerational study. Age of puberty acquisition,i.e., preputial separation(PPS) and vaginal opening(VO), was examined in male and female offspring, respectively. When compared to controls, a slight, but statistically significant delay in puberty acquisition was observed in females but not in males. WM-induced differences in the age at puberty acquisition were compared to those reported in S–D rats administered either a defined mixture(DM) of nine regulated DBPs or individual DBPs. Regression models were developed using individual animal data on age at PPS or VO from the DM study. Puberty acquisition data reported in the WM and individual DBP studies were then compared with the DM models. The delay in puberty acquisition observed in the WM-treated female rats could not be distinguished from delays predicted by the DM regression model, suggesting that the nine regulated DBPs in the DM might account for much of the delay observed in the WM. This method is applicable to mixtures of other types of chemicals and other endpoints.     

A new technique helps to uncover unknown peptides and disinfection by-products in water

正Environmental water samples can be extremely complex,with potentially thousands of molecules that can derive from natural organic matter(NOM)and thousands that derive from anthropogenic contaminants.As complex as these samples are,drinking water can be even more complex.Due to disinfectants that are used to treat drinking water(e.g.,chlorine,chloramines,     

The impact of iodinated X-ray contrast agents on formation and toxicity of disinfection by-products in drinking water

The presence of iodinated X-ray contrast media (ICM) in source waters is of high concern to public health because of their potential to generate highly toxic disinfection by-products (DBPs). The objective of this study was to determine the impact of ICM in source waters and the type of disinfectant on the overall toxicity of DBP mixtures and to determine which ICM and reaction conditions give rise to toxic by-products. Source waters collected from Akron, OH were treated with five different ICMs, including iopamidol, iopromide, iohexol, diatrizoate and iomeprol, with or without chlorine or chloramine disinfection. The reaction product mixtures were concentrated with XAD resins and the mammalian cell cytotoxicity and genotoxicity of the reaction mixture concentrates was measured. Water containing iopamidol generated an enhanced level of mammalian cell cytotoxicity and genotoxicity after disinfection. While chlorine disinfection with iopamidol resulted in the highest cytotoxicity overall, the relative iopamidol-mediated increase in toxicity was greater when chloramine was used as the disinfectant compared with chlorine. Four other ICMs (iopromide, iohexol, diatrizoate, and iomeprol) expressed some cytotoxicity over the control without any disinfection, and induced higher cytotoxicity when chlorinated. Only iohexol enhanced genotoxicity compared to the chlorinated source water.     

Disinfection By-Products in Drinking Water, Recycled Waterand Wastewater: Formation, Detection, Toxicity and HealthEffects: Preface

<正>The disinfection of drinking water was an outstanding(and perhaps the most important)public health achievement of the 20~(th) century.According to the United Nations World Health Organization,over 4 billion people have access to     

Disinfection byproducts and halogen-specific total organic halogen speciation in chlorinated source waters——The impact of iopamidol and bromide

This study investigated the speciation of halogen-specific total organic halogen and disinfection byproducts(DBPs) upon chlorination of natural organic matter(NOM) in the presence of iopamidol and bromide(Br~-).Experiments were conducted with low bromide source waters with different NOM characteristics from Northeast Ohio,USA and varied spiked levels of bromide(2-30 μmol/L) and iopamidol(1-5 μmol/L).Iopamidol was found to be a direct precursor to trihalomethane(THM) and haloacetic acid formation,and in the presence of Br~-favored brominated analogs.The concentration and speciation of DBPs formed were impacted by iopamidol and bromide concentrations,as well as the presence of NOM.As iopamidol increased the concentration of iodinated DBPs(iodo-DBPs) and THMs increased.However,as Br~-concentrations increased,the concentrations of nonbrominated iodo-and chloro-DBPs decreased while brominated-DBPs increased.Regardless of the concentration of either iopamidol or bromide,bromochloroiodomethane(CHBrClI) was the most predominant iodo-DBP formed except at the lowest bromide concentration studied.At relevant concentrations of iopamidol(1 μmol/L) and bromide(2 μmol/L),significant quantities of highly toxic iodinated and brominated DBPs were formed.However,the rapid oxidation and incorporation of bromide appear to inhibit iodoDBP formation under conditions relevant to drinking water treatment.