to the editor: I appreciated the informative editorial, "Health Effects from Pesticide Exposure,"¹ by Dr. Calvert.

Recent research links chronic low-level pesticide exposure to many health problems. Pesticide exposure was linked to significantly higher wheezing rates in a study in the United States of 20,468 farmers.² Long-term agricultural pesticide exposure also has been linked to slower peripheral nerve velocities³ and significantly poorer memory, concentration, motor speed, and color vision.⁴ Other recent studies have linked chronic low-level pesticide exposure with higher rates of Alzheimer's and Parkinson's disease⁵ and higher rates of impotence.⁶

I hope that American Family Physician will continue to provide updated articles on health effects of pesticides and other environmental hazards.

in reply: Curtis raises important concerns about chronic health effects that may be related to pesticide exposure. We agree that the evidence supporting these associations continues to build. However, much of this evidence is based on epidemiologic studies. All epidemiologic studies have limitations, and no one study is sufficient to support a causal link between pesticide exposure and chronic illness. This includes the findings from the Agricultural Health Study,¹ which is a large prospective cohort study consisting of approximately 90,000 subjects who are pesticide applicators or spouses of pesticide applicators. This study will be an important source of information on health outcomes associated with pesticide exposure. Recent findings from this study,¹ which is scheduled to continue through the year 2020, are available online at: http://www.aghealth.org/publications.html. The uncertainty regarding pesticide toxicity does not mean we can ignore the information we have. As was stated in my editorial,² the reduction of pesticide exposure should be encouraged, including adoption of integrated pest management practices,³ compliance with all pesticide label instructions, and, when necessary, revision of public policies and regulations.