Background

Poly-brominated diphenyl ethers (PBDEs) and heavy metals are persistent pollutants in Yangtze River basin, China and also around the globe. In the exposure reality, they may have sequential exposures and long-term outcomes. Yet, the effects combining these two aspects remained largely unexplored. At present, the effects of 2,2′,4,4′-tetra-brominated diphenyl ether (BDE47) and lead (Pb) on Caenorhabditis elegans were studied with two sequential arrangements. One was first exposure to BDE47 and then to Pb (or vice versa) in one generation, and the other one was an early exposure to BDE47 in the parent generation (F0) and then a later exposure to Pb in the offspring (F1) (or vice versa).

Results

On growth, sequential Pb-BDE47 exposure caused inhibition in exposure but stimulation in recovery, showing similarity to individual Pb results. Meanwhile, the opposite sequential BDE47-Pb exposure showed inhibition in both exposure and recovery, similar to those of individual BDE47 results. On behavior, the effects of sequential exposure were significantly different from individual results without any similarity. In transgenerational effects, F0 Pb exposure with F1 BDE47 exposure (Pb-F1-BDE47) inhibited growth, similar to the transgenerational results of individual Pb exposure. Meanwhile, the recovery effects were similar to the transgenerational results of individual BDE47. At the same time, Pb-F1-BDE47 exposure significantly hindered the recovery of behavior while the opposite BDE47-F1-Pb exposure resulted in different results. The behavioral effects in F1 showed negative correlation with the contents of γ-aminobutyric acid (GABA), while those in F1 were positively correlated with the activities of acetylcholine esterase (AChE).

Conclusions

Sequential exposure to BDE47 and Pb within one generation or over generations showed significant different effects from individual results. Further studies are still needed to investigate the toxicity patterns and underlying mechanisms.