Introduction to epidemiological approaches to mixtures health effects

Risk assessment of mixtures in epidemiology are challenging due to inherent power issues. Mixtures from an epidemiological perspective can be defined as either exposures occurring at the same time having similar effects on e.g. organ level, mode of action and mechanism of action; or protracting exposures. The risk of these mixtures may be different depending on both their quantitative and qualitative composition. The joint effect of relevant components of a mixture can be estimated by combining exposures in a supervised or unsupervised manner, or by explicit estimation of interactions of individual components. Combining exposures assumes equal mechanism and equal potency (within a group). The estimation of the interaction between two chemicals can be either additive or multiplicative, with simultaneous or non-overlapping exposures. When measuring the joint effects in human data, measurements of biological perturbations and allostatic load are promising but still in its infancy.