We get excited about sharing new research that could have an impact on health. And we really appreciate it when our readers raise practical questions about the implications of the study. A recent report in JAMA Internal Medicine showed that people who had been exposed to high levels of pyrethroid pesticides were at higher risk for heart problems and early death. Consequently, we were pleased when an astute visitor asked about avoiding insecticides in tick-resistant clothing. We only wish our answer could be more definitive.
Avoiding Insecticides in Treated Clothing:
Q. I read a news story on your website about pyrethroid insecticides harming the heart. I use permethrin-treated clothing to keep ticks off when I work outside to reduce my risk of Lyme disease.
Do you know if people absorb such chemicals through their skin? These clothes work great to keep ticks off, but my heart is important too!
Pesticides and Heart Disease:
A. The research you refer to was published in JAMA Internal Medicine (Dec. 30, 2019). People exposed to such insecticides were at greater risk of dying from cardiovascular disease. In a comparison of people with the highest levels of pyrethroid metabolites in the urine to those with the lowest levels, death rates in 14 years were 11.9 percent and 8.5 percent respectively. Most of the difference was due to heart disease and strokes. There was no difference in the risk of cancer.
Is Permethrin-Treated Clothing Hazardous?
Unfortunately, there is not much research on whether or not permethrin-treated clothing poses a problem. Some studies show marginal absorption. A study of the German military, however, showed that soldiers wearing permethrin-impregnated uniforms had high levels of permethrin metabolites in their urine (Occupational and Environmental Medicine, Feb. 2014). In another study, scientists issued ordinary work pants or permethrin-treated pants to German forestry workers (Journal of Exposure Science & Environmental Epidemiology, Jan-Feb. 2016). Those wearing the treated pants had significantly higher levels of permethrin metabolites. Nonetheless, these were below the proposed WHO threshold for acceptable daily exposure.
On the other hand, North Carolina state and county park employees volunteered for a different trial (Parasites & Vectors, Jan. 23, 2019). For three months, they wore long-lasting permethrin-impregnated clothing to work. The scientists monitored urinary levels of three different permethrin metabolites. In addition, they tested the ability of the socks and pants to kill ticks at the end of the time. That remained high.
In summary, the investigators concluded:
“The estimated absorbed dosage of permethrin was well below the U.S. EPA level of concern, suggesting that LLPI clothing can be used safely by outdoor workers for tick bite prevention.”