Herbicides and pesticides synergistically interact at low concentrations in complex mixtures.

Assessing a complex mixture of pesticides at the impacted sites has been challenging for risk assessors for 50 years. The default assumption is that at low concentrations, pesticides interact additively with one another; thus, the risk posed by each component of a complex mixture could be simply added up. The EPA interaction-based hazard index (HIInteraction) modifies this assumption using a binary weight-of-evidence (BINWOE). However, data gaps often preclude HIInteraction use at most sites. This study evaluated these assumptions using the BINWOE to estimate the hazard index (HI) of select pesticide mixtures. The lack of in vivo binary interaction data led us to use a cell line, SH-SY5Y, to obtain the data necessary for the BINWOE approach. In the risk assessment, we considered the most active exposure scenario inhaling a mixture of volatile pesticides from contaminated soil and groundwater. The potential interactions between pesticides in 15 binary mixtures were investigated using the MTT assay in SH-SY5Y cells. Our findings showed that 60% of the binary mixtures elicited synergism (in at least one concentration), 27% displayed antagonism, and 13% showed additive effects in SH-SY5Y cells. Combining human safety data with in vitro interaction data indicated that adults and toddlers were at the highest risk when considering industrial and commercial land use, respectively, compared to other subpopulations. Incorporating interaction data into the risk assessment either increased the risk by up to 20% or decreased the risk by 2%, depending on the mixture. Our results demonstrate the predominant synergistic interactions, even at low concentrations, altered risk characterization at the complex operating site. Most concerning, organochlorine pesticides with the same mechanism of action did not follow dose additivity when evaluated by SH-SY5Y cell lines. Based on our observations, we caution that current HI methods based on additivity assumptions may underestimate the risk of organochlorine mixtures.

Study on the oxidative stress status among cement plant workers.

The cement industry is considered as a major pollution problem because of dust and particulate matter emitted at various steps of cement production. In the present study, volunteer male workers from a cement factory were studied for oxidative and nitrosative stress biomarkers in relation to their serum levels of aluminum (Al) and chromium (Cr). The subjects were divided into two groups of direct and indirect exposure. Subject who worked in production steps were considered as direct exposure group, and those who worked in administration building were considered as indirect exposure group. For comparison, healthy subjects at the same age and socioeconomic status were tested as a control group. Serum levels of lipid peroxidation (LP), total antioxidant capacity (TAC), total thiol molecules (TTM), and nitric oxide (NO) as well as Al and Cr were measured. The results indicated a significant increase in Al (P = 0.001) and Cr (P = 0.009) levels in direct-exposed workers in comparison to healthy control group. Further, a significant increase in Al (P = 0.002) and Cr (P = 0.009) levels was observed in direct-exposed workers as compared to indirect-exposed one. Serum levels of TTM and TAC were significantly lower in both direct- and indirect-exposed groups in comparison to healthy control group (P = 0.00). Serum TTM and TAC were significantly lower in direct-exposed workers as compared to indirect-exposed ones (P = 0.00 and P = 0.024, respectively). There was no significant difference on the level of LP and NO among groups. A correlation was found between serum level of Cr, TAC, and platelets between direct- and indirect-exposed groups (P < 0.05). Further correlation was found among serum level of Cr and those of TTM, platelets, and chronic disease (P < 0.05). Chronic disease had a significant influence adjusted to other predictor variables on the post-shift values of Al (P < 0.05). Although plasma levels of Al and Cr were found in normal ranges, analyses confirm their role in impairment of TMM and TAC.