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Atomic charges of individual reactive chemicals in binary mixtures determine their joint effects: An example of cyanogenic toxicants and aldehydes

Authors

  • Dayong Tian,

    1. State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China
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  • Zhifen Lin,

    Corresponding author
    1. State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China
    • State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
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  • Daqiang Yin,

    1. Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, China
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  • Yalei Zhang,

    1. Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, China
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  • Deyang Kong

    1. Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection of PRC, Nanjing, China
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Abstract

Environmental contaminants are usually encountered as mixtures, and many of these mixtures yield synergistic or antagonistic effects attributable to an intracellular chemical reaction that pose a potential threat on ecological systems. However, how atomic charges of individual chemicals determine their intracellular chemical reactions, and then determine the joint effects for mixtures containing reactive toxicants, is not well understood. To address this issue, the joint effects between cyanogenic toxicants and aldehydes on Photobacterium phosphoreum were observed in the present study. Their toxicological joint effects differed from one another. This difference is inherently related to the two atomic charges of the individual chemicals: the oxygen charge of -CHO (Oaldehyde toxicant) in aldehyde toxicants and the carbon-atom charge of a carbon chain in the cyanogenic toxicant (Ccyanogenic toxicant). Based on these two atomic charges, the following QSAR (quantitative structure–activity relationship) model was proposed: When (Oaldehyde toxicant − Ccyanogenic toxicant) > −0.125, the joint effect of equitoxic binary mixtures at median inhibition (TU, the sum of toxic units) can be calculated as TU = 1.00 ± 0.20; when (Oaldehyde toxicant − Ccyanogenic toxicant) ≤ −0.125, the joint effect can be calculated using equation image (n = 40, r = 0.887, SE = 0.195, F = 140, p < 0.001, q2Loo = 0.748; SE is the standard error of the regression, F is the F test statistic). The result provides insight into the relationship between the atomic charges and the joint effects for mixtures containing cyanogenic toxicants and aldehydes. This demonstrates that the essence of the joint effects resulting from intracellular chemical reactions depends on the atomic charges of individual chemicals. The present study provides a possible approach for the development of a QSAR model for mixtures containing reactive toxicants based on the atomic charges. Environ. Toxicol. Chem. 2012;31:270–278. © 2011 SETAC

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