While agro-chemicals such as pesticides, fungicides, and herbicides are often promoted as inputs that increase agricultural productivity by limiting a range of pre-harvest losses, their use may have negative human health and labor productivity implications. We explore the relationship between agro-chemical use and the value of crop output at the plot level and a range of human health outcomes at the household level using nationally representative panel survey data from four Sub-Saharan African countries where more than ten percent of main season cultivators use agrochemicals. We find that agro-chemicals use is associated with increased value of harvest, with similar magnitudes across three of the four countries under study, but is also associated with increases in costs associated with human illness, including increased health expenditures related to illness and time lost from work due to sickness in recent past. We motivate our empirical work with a simple dynamic optimization model that clearly shows the role that farmer understanding of these feedbacks can play in optimizing the use of agro-chemicals. The central role of information in determining that optimum underscores the role of agricultural and public health extension as modern input intensification proceeds in the region.