In this paper, a simple willingness to pay (WTP) model that shows the theoretical relationships among three valuation approaches that can be used to measure changes in health resulting from pollution is developed. The three valuation approaches considered are the contingent valuation (CV), cost of illness (COI) and the defensive behaviour approaches. After showing the relationships between the three valuation approaches, the model demonstrates that the CV approach exceeds the COI and the defensive behaviour approaches. The theoretical results are supported by field survey data. The pollution referred to in this paper is direct exposure to pesticides by farmers during handling and spraying on their farms.