Synergistic Toxic Effects Of Nonylphenol And Nonylphenol Ethoxylate On Moina Macrocopa

Environmental hormones are called “ecoestrogen” or “environmental endocrine disruptors”.They are a kind of exterior contaminant for animals and human body. Because environmentalhormones may act as estrogens in organisms, it can disturb normal endocrine functions. Jointtoxic effect means the synthetical effect of two or more than two chemicals act simultaneouslyon the organism at the same time. Nonylphenol （NP） are widely used in chemical industries, themajor source of NP in the aquatic environment is the degradation of Nonylphenol ethoxylates（NP_nEO）. As an endocrine disruptor, NP was found to mimic the effects of natural hormone17β-estradiol. In addition, NP has carcinogenic, teratogenic and mutagenic potential. Aim toexplore the synergistic toxic effects of NP₁₀EO and its primary degradation product NP on Moinamacrocopa, the acute and chronic toxic effects of either NP₁₀EO, or NP, or a combination of thetwo chemicals on Moina macrocopa, were studied in laboratory. In joint toxicity test, the extentof toxic interactions was evaluated by converting mixture LC₅₀estimates to toxic unit （TU）.Based on the24h LC₅₀values for individual NP₁₀EO and NP acute toxicity test, one TU isdefined as that:0.5×LC₅₀（NP）+0.5×LC₅₀(NP₁₀EO). In chronic toxicity test, the survivorship ofM. macrocopa, the breeding frequency, the total neonates number, the time to the first brood, thebody length of the F0generation and larvae of M. macrocopa were recorded. The resultsindicated that:（1） NP was more toxic to M. macrocopa than NP₁₀EO. The24h and48h LC₅₀values were0.154,0.065mg·L^-1for NP, and3.37,2.11mg·L^-1for NP₁₀EO, respectively.（2） The24h and48h LC₅₀values of binary mixtures of NP₁₀EO and NP were0.646and0.291TUs,respectively. The results suggest that NP₁₀EO and NP can interact synergistically.（3） Both ofthese two chemicals decreased the survivorship, the breeding frequency, the total neonatesnumber, and shortened the body length of F0generation and larvae of M. macrocopa.（4）Combined exposure to NP₁₀EO and NP caused marked decreases in reproduction and growth inF0generation, and it substantially shortened the body length of larvae. The synergisticrelationship of NP₁₀EO and NP to M. macrocopa suggests that pollution with these chemicalsposes adverse effects on aquatic ecosystem. The parent compounds and their degradationproducts may frequently coexist in natural waters, which result in an increase of overall toxicity as compared to a single compound. The synergistic toxic effects, therefore, should be taken intoaccount when assessing the toxicity of organic contaminants to aquatic organisms.