Products used to combat agricultural pests, Zika impact motor skills in infants
New research finds that two chemical compounds commonly found in household cleaning and personal hygiene products cause birth defects in rodents.
Researchers from the Edward Via College of Osteopathic Medicine (VCOM) and the Virginia-Maryland College of Veterinary Medicine at Virginia Tech – both in Blacksburg, VA, United States (U.S.), – set out to examine the effect of a common type of chemicals in mice and rats.
The first author of the study – published in the journal Birth Defects Research – is Terry Hrubec, associate professor of anatomy at VCOM and research assistant professor in the Department of Biomedical Sciences and Pathobiology at the Virginia-Maryland College of Veterinary Medicine.
Hrubec and colleagues investigated the effect of a large class of common household chemicals called “quaternary ammonium compounds,” or “quats.”
Due to their antimicrobial and antistatic properties, these products are routinely used as disinfectants in the form of household cleaning products, laundry detergent, and fabric softener. They are also used as preservatives in personal hygiene products, such as shampoo, conditioner, and eye drops.
Hrubec and team specifically looked at two quats: alkyldimethylbenzyl ammonium chloride (ADBAC) and didecyldimethyl ammonium chloride (DDAC).
These two quats are used in combination in common cleaning products. For the experiment, the researchers introduced the substances in the vivarium of both mice and rats.
The study found that neural tube defects (NTDs) increased proportionally with the ambient exposure to the chemicals. NTDs are birth defects that take place in the first month of pregnancy, affecting the brain, spine, or spinal cord of the fetus.
Also, a chemical currently being used to ward off mosquitoes carrying the Zika virus and a commonly used insecticide that was threatened with a ban in the United States have been associated with reduced motor function in Chinese infants, a University of Michigan, United States (U.S.), study found.
Researchers at the U-M School of Public Health and U-M Center for Human Growth and Development tested children in China and found exposure to the chemical naled via their mothers during pregnancy was associated with three-four percent lower fine motor skills scores at age nine months for those in the top 25 percent of naled exposure, compared to those in the lowest 25 percent of exposure. Infants exposed to chlorpyrifos scored two-seven percent lower on a range of key gross and fine motor skills.
Girls appeared to be more sensitive to the negative effects of the chemicals than boys.
Naled is one of the chemicals being used in several U.S. states to combat the mosquito that transmits Zika. Chlorpyrifos, around since the 1960s, is used on vegetables, fruit and other crops to control pests.
The study titled “Prenatal naled and chlorpyrifos exposure is associated with deficits in infant motor function in a cohort of Chinese infants” is published in journal Environment International.
Both are insecticides called organophosphates, a class of chemicals that includes nerve agents like sarin gas. They inhibit an enzyme involved in the nerve signaling process, paralyzing insects and triggering respiratory failure. However, they may adversely impact health through other mechanisms at lower exposure levels that are commonly encountered in the environment.
In the children studied, naled affected fine motor skills or the small movements of hands, fingers, face, mouth and feet. Chlorpyrifos was associated with lower scores for both gross (large movements of arms and legs) and fine motor skills.
The only studies to date on naled health impacts have taken place in occupational settings, not with exposure in the general population, Silver says.
Previous chlorpyrifos research has found ties to delayed motor development in children and a host of health issues for those who handle the chemical, including nausea, dizziness and convulsions.
The U-M researchers examined the umbilical cord blood of about 240 mothers, looking for exposure to 30 different organophosphate insecticides, five of which showed up in at least 10 percent of the samples. In addition to naled and chlorpyrifos, they found methamidophos, trichlorfon and phorate.
The cord blood was gathered from 2008-11 as part of a cohort study designed by co-author Betsy Lozoff of the U-M Center for Human Growth and Development to investigate the relationships between iron deficiency and infant neurodevelopment.
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