- Environmental toxins play a vital role in decreasing the age of onset of puberty for both boys and girls and early occurrence of puberty is associated with various health risks during adulthood.
- Pyrethroids, a class of pesticides interfere with the body's hormones and its presence in humans can be traced by a metabolite or molecule, called 3-phenoxybenzoic acid (3-PBA), in the urine.
- Boys who were exposed to pyrethroids were found to have higher levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), that spur the production of testosterone and thus speed up puberty in them.
Environmental exposure to common pesticides may cause boys to reach sexual maturity earlier.
The class of pesticides studied, pyrethroids, accounts for more than 30% of global insecticide use, said Jing Liu, Ph.D., lead investigator and an associate professor at Zhejiang University in Hangzhou, China. They are commonly sprayed indoors and outdoors to kill mosquitoes and other insects, and used on crops.
‘Chemicals should be prudently assessed for their risks to children's health. Early onset of puberty in boys is found to be linked to a class of household pesticides.’
Humans are mostly exposed to pyrethroids from food and residential use. Evidence of recent exposure to pyrethroid in humans can be traced by the presence of a metabolite, or molecule, called 3-phenoxybenzoic acid (3-PBA), in the urine. These chemicals are known endocrine-disrupting chemicals that interfere with the body's hormones.
"We recognize pyrethroids as a new environmental contributor to the observed trend toward earlier sexual maturity in boys," Liu said.
The average age at which a boy's body matures into an adult's is between 9 and 14 years of age, according to the Hormone Health Network.
Many factors including environmental toxins, contribute to the decreasing age of onset of puberty for both boys and girls. Early occurrence of puberty increases various health risks during adulthood, including testicular cancer in men and breast cancer in women. Early puberty can also stunt growth and cause behavioral problems.
Effect of Pyrethroids
In the study that included 463 Chinese boys ages 9 to 16 years, the research team found that a 10% increase in 3-PBA was associated with a 4% increase in the boys' levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are responsible for the production of testosterone in males.
The odds of a boy being at an advanced stage of genital development were raised by 73% to 110%, if the levels of urinary 3-PBA were high.
The research team also tested how pyrethroids altered the timing of puberty in mice.
Because it is difficult to test the cause of environmental risk factors in humans, the researchers sought to identify how pyrethroids alter the timing of puberty in animals.
The male mice were exposed to cypermethrin, a widely used pyrethroid insecticide, at the relevant levels that are present in humans. This resulted in an accelerated onset of puberty. Liu said they demonstrated that cypermethrin had a direct effect by inducing testosterone formation and interfering with intracellular processes that are critical to male sexual development.
"Given the growing use of pyrethroid insecticides, we must prudently assess these chemicals for their risks to children's health," Liu said.
The study results will be presented at the Endocrine Society's 99th annual meeting in Orlando, Florida.