Effects of errors in the measurement of agricultural exposures.

The measurement error in agricultural exposures can be expected to be substantial given the nature of agricultural production. Agricultural work is often seasonal, and exposures to chemical and biological agents vary in a temporal sense due to the task variety and intermittent nature of most agricultural exposures. Exposure patterns are also often complex in terms of the specific agents involved and entail mixed exposure situations. However, farmers often have stable careers and tend to stay in the same working and living environment. Their conservative attitudes also make them reliable sources of past production patterns, machinery, and chemical use. To reduce the measurement error that potentially obscures relations between agricultural exposures and health outcomes, more effort should be put into revealing actual determinants of agricultural exposures. Knowledge of these determinants can be used in questionnaires for retrospective exposure assessment, either in studies of the general population or within agricultural populations, and can be used to predict exposure more reliably.