Pyriproxyfen Exposure and Its Impact on Human Health

Understanding the developmental toxicity from exposure to pyriproxyfen

The Zika virus became a national health concern for many Americans in 2016. With over 5,000 reported cases, the World Health Organization declared it an epidemic. This mosquito-borne disease, which is rare in the continental United States, spread to nearly every state, resulting in actions to target mosquito populations and mitigate the disease. 

What is the Zika Virus?

Zika is common in tropical and sub-tropical regions, including Asia, South America, the Caribbean, and the Pacific Islands. It spreads to humans by the bite of an infected Aedes mosquito, sexual intercourse, or childbirth. Mild symptoms include a fever, rash, muscle pain, joint pain, headaches, and red eyes. In severe cases, infected pregnant women can pass the virus to their offspring during childbirth. Zika can also cause serious birth defects, including microcephaly, a condition that causes babies to be born with a small head. Babies with microcephaly often have learning disabilities due to their underdeveloped brains. 

Using Pyriproxyfen to Combat the Spread of Zika Virus

Despite the first documented case in the 1940s, there is currently no vaccine or medical prevention for the Zika virus. Consequently, governments rely on the use of pesticides like pyriproxyfen to stop the reproduction and spread of Aedes mosquitoes carrying the disease. 

Pyriproxyfen is an insect growth regulator that attacks the hormonal system of larvae. It prevents juvenile insects from maturing to adults, blocking reproduction. Since its introduction to the market in the 1990s, pyriproxyfen has been deemed as a safe chemical with a low acute oral toxicity in mammals. It is found in over 300 registered pesticide products. It is also used as a topical flea prevention medicine for dogs and cats and to protect agricultural crops.

While the obvious signs of toxicity seem negligible, little has been studied about pyriproxyfen’s long-term effects in humans and the environment. Because the chemical mimics natural insect hormones, many researchers suggest that it has the potential to disrupt thyroid hormones and affect brain development in children. Pyriproxyfen has also been detected in aquatic environments, and recent studies have revealed its endocrine-disrupting properties in Zebra fish. 

Laboratory Analysis of Pyriproxyfen's Effects Post-Zika Outbreak

Following the Zika virus outbreak, RTI helped the National Toxicology Program (NTP) study the effects of pyriproxyfen through in-vivo and in-vitro studies. Our team conducted chemical procurement and characterization, dose formulations, and biosample analyses. Ultimately under the conditions of the studies, there was no evidence linking pyriproxyfen to fetal abnormalities. This work allowed NTP to further understand pyriproxyfen and its safety as a commonly used pesticide. 

Learn more about RTI’s Analytical Laboratory.