Two chemicals found in household cleaning products led to neural tube defects in mice and rats.
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 - 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.
The effects of disinfectants in rodents
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.
Male and female mice received ADBAC plus DDAC combined, in the form of a commercial disinfectant.
They received the substance in their food, as well as being exposed to it in the atmosphere.
The rodents were administered 60 or 120 milligrams of the substance per kilogram of body weight (mg/kg), daily, in their food, or 7.5, 15, or 30 mg/kg of body weight, administered by oral gavage - a precise method of oral dosing commonly used in rodent studies.
Finally, the rodents were also exposed to the quats ambiently, as the disinfectant was used in their room.
Hrubec and colleagues assessed the embryos on the 10th day of pregnancy, as well as on the 18th day when they looked for "gross and skeletal malformations."
Chemicals caused neural tube defects
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.
Significantly, exposing the males to the chemical-laden atmosphere in the room alone was enough to cause reproductive defects. In fact, ambient exposure to the chemical had a larger influence on NTDs than oral dosing.
"Birth defects were seen when both males and females were exposed, as well as when only one parent was exposed [...]," says Hrubec.
"The fact that birth defects could be seen when only the father was exposed means that we need to expand our scope of prenatal care to include the father [...]. We also observed increased birth defects in rodents for two generations after stopping exposure."
The results confirm previous studies conducted by Hrubec and team. One such study found that the same chemicals affect reproductive performance in mice, and a follow-up study indeed confirmed that quats led to a decline in sperm counts in males and ovulation in female rodents.
"These chemicals are regularly used in the home, hospital, public spaces, and swimming pools," says Hrubec. "Most people are exposed on a regular basis."
"Since rodent research is the gold standard in the biomedical sciences, this raises a big red flag that these chemicals may be toxic to humans as well," she adds.
Hrubec suggests that an epidemiological study should investigate whether humans who are routinely exposed to these chemicals - such as those working in hospitals or restaurants - have trouble getting pregnant or are more likely to have children with birth defects.
Quats are currently regulated by the United States Environmental Protection Agency.