Toxic effects of the joint exposure of decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA) on soil microorganism and enzyme activity

• BDE209 and TBBPA can cause visible changes in soil microbial population and enzyme activity.
• The response sensitivity of soil microorganism followed the order: fungi > bacteria > actinomycete.
• Urease was more susceptive to the two BFRs than catalase and saccharase activities.
• The interaction of the two chemicals was mainly antagonistic effect.

Decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA) are the main contaminants at e-waste recycling sites, and their potential toxicological effects have received extensive attention. However, the impact on soil culturable microbial population and enzyme activity of joint exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the eco-toxicological response in the joint presence of BDE209 and TBBPA for the first time. The results have demonstrated some notable toxic effects due to long-term exposure to either or both contaminants. The inhibition ratios of microbial populations increased with incubation time and increasing concentrations of BDE209 or TBBPA following certain dose–response relationships and time-effect trends. The response sensitivity sequence was fungi > bacteria > actinomycete. The influence of the two chemicals on soil enzymes reached peak values on day 7, and highly significant differences (P < 0.01) were observed compared to the controls. Urease was more susceptive to the two chemicals than catalase and saccharase activities. Generally, the joint toxicity of both contaminants on soil microbes, catalase or saccharase activities indicated antagonistic effects, while, as for urease activity, addition role was dominant. Such observations have provided the useful information of potential ecological effects of brominated flame retardants contamination in the environment.