Inorganic arsenic (iAs) and methylmercury (MeHg) are both neurotoxicants; however the joint impacts due to co-exposure are uncertain. Adult parental (F0) zebrafish (Danio rerio) were co-exposed to MeHg (through diet, 1 ppm) and iAs(III) (through water, 0.05 mg/L or 0.5 mg/L) (6 treatment groups). F1 larvae were exposed to both chemicals through maternal transfer only; F2 were unexposed. Neurobehavioral outcomes were assessed in F0 and F1 adults, and F1 and F2 larvae. The mRNA levels of zas3mt and six DNA methyltransferases were analyzed in F0 livers, the main site for metabolism of iAs(III) and MeHg. Neurobehavioral outcomes differed between fish co-exposed to iAs + MeHg compared to single-exposed or unexposed fish, suggesting additive impacts due to co-exposure; however, these results were limited to F0 adults and F1 larvae. Higher expression of zas3mt, dnmt3ab and dnmt3bb.2 in single-exposed As fish or unexposed fish, compared to MeHg-exposed (or co-exposed with iAs) fish suggested differences in metabolism.
