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Your Environment. Your Health.

Methods to Study Chemical Mixtures in the Environment

Marianthi-Anna Kioumourtzoglou, Sc.D.
Columbia University
R01ES028805, R01ES028811, R01ES028800, P30ES009089, P30ES000002, P30ES023515, U2CES026555, T32ES007322, T32ES007142, F31ES030263

NIEHS grantees demonstrated how modern statistical methods can be used to address a range of distinct questions about exposures to mixtures of chemicals in the environment. According to the authors, no single method can answer all mixtures questions, but with a well-defined research question and appropriate use of statistical approaches, scientists can explore complex relationships between environmental mixtures and adverse health outcomes.

The researchers evaluated the impact of exposure to a mixture of persistent organic pollutants (POPs) on leukocyte telomere length (LTL), a potential mechanism of underlying risk of developing cancer. With information on 18 POPs and LTLs among 1,003 U.S. adults, the researchers used unsupervised methods, which recognize patterns, to identify common exposure sources and shared behaviors among similarly exposed participants. They also employed supervised learning techniques, which focus on relationships between known variables, to identify potentially toxic agents, synergistic activities among the mixture’s components, and to estimate the overall mixture effect.

The researchers showed that results using unsupervised and supervised approaches might not be directly comparable but were generally consistent with each other and with biologically driven results. Using different approaches, they observed an overall mixture effect on LTLs but no interactions among chemicals that would amplify the effects. They also identified individual chemicals that were toxic across the different analyses, including specific forms of polychlorinated biphenyls and furans. The researchers suggested their methods could be used as a toolbox to guide method selection based on specific research questions about mixtures.

Citation: Gibson EA, Nunez Y, Abuawad A, Zota AR, Renzetti S, Devick KL, Gennings C, Goldsmith J, Coull BA, Kioumourtzoglou MA. 2019. An overview of methods to address distinct research questions on environmental mixtures: an application to persistent organic pollutants and leukocyte telomere length. Environ Health 18(1):76.

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