coexposure

Coexposure refers to exposure to two or more environmental agents, such as chemicals, physical factors, or biological agents, occurring at the same time or in sequence. It is a central concern in toxicology, epidemiology, and environmental health because interacting agents can modify health risks in ways that differ from single-agent exposures. Interactions among coexposures are commonly categorized as additive, synergistic, or antagonistic. In additive effects the combined impact equals the sum of individual effects; in synergistic effects the combined impact exceeds the sum; antagonistic effects diminish the overall impact. Some relationships are potentiating, where one exposure amplifies the effect of another. Risk assessment for coexposures often uses methods such as cumulative risk assessment, hazard indices, or more advanced mixture models to estimate the combined risk.

Common contexts include air pollution with heat or noise, chemical mixtures in consumer products, occupational exposure to solvents, metals, or pesticides, and pharmacological drug interactions. Coexposure assessment presents challenges due to high dimensionality, variability in exposure timing and dose, and limited data on interactions. Researchers use epidemiologic studies, toxicology experiments, high-throughput screening, and computational modeling to characterize risks and identify susceptible populations.

Policy and public health implications include developing guidelines for safe mixtures, improving monitoring of multi-agent exposures, and creating regulatory frameworks that address combined risks rather than single chemicals alone. This neutral overview highlights coexposure as a foundational concept in understanding real-world environmental health risks.