Quats, a family of chemicals common in soaps and other household products, impair nervous-system development in both rats and mice, a new study warns. The type of neural tube defects include spina bifida, in which the fetal spinal column doesn't close completely, and anencephaly, which is the absence of a major portion of the brain.
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Many manufacturers use quaternary ammonium compounds, or quats, because of their antimicrobial and antistatic properties. If they're so bad for rodents, what are the chances that they're hurting us?
"It is always difficult to extrapolate from animal studies directly to humans," cautions the lead author of the landmark study, Dr Terry Hrubec of the Edward Via College, Virginia, in an email to Haaretz. "Individual species respond differently to chemicals, and a specific chemical may be more toxic to one species over another. However, rodent studies are the gold standard for testing the safety of pharmaceuticals and chemicals. The fact that we see an adverse effect in both mice and rats raises a big red flag that these chemicals may be toxic to humans and indicates that studies should be conducted to evaluate their safety in humans."
Meanwhile, quats are widespread in everything from cleansers and laundry soap, fabric softener and shampoo, disinfectants, hair conditioner, and are even found in eye drops, say the authors of the study "Ambient and dosed exposure to quaternary ammonium disinfectants causes neural tube defects in rodents".
"These chemicals are regularly used in the home, hospital, public spaces, and swimming pools," said Hrubec, who worked on the study with the Virginia Tech veterinary school. "Most people are exposed on a regular basis."
Two commonly used quats are alkyldimethylbenzyl ammonium chloride (ADBAC) and didecyldimethyl ammonium chloride (DDAC). These were the substances the scientists tested.
Mice were exposed to ambient concentrations through "normal use" of the cleaner in the mouse room, the professor explains. "This exposure could be comparable to what a person might receive in a medical setting or food service setting where disinfection and decreased spreading of germs is important, although we have not tested this," Hrubec stresses, and clarifies, "The concentration used when mice were dosed in the feed was higher than a person would experience with normal use of the disinfectant."
In evaluations on gestational day 10 and gestational day 18, the scientists found increased incidence of neural tube defects.
Moreover, it isn't just the mother's exposure that counts. "Birth defects were seen when both males and females were exposed, as well as when only one parent was exposed," said 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." (Yes, they used quat-free females to test the effect of quats on the males.)
They also observed increased birth defects in rodents for two generations after stopping exposure, she says.
An earlier study by Hrubec found that quats led to reproductive declines in mice: sperm count and ovulation both fell, which begs the thought that quats might be contributing to the increasing incidence of human infertility, says the team.
Even if we don't eat them with a spoon, quats abound around us. "Chemicals can get into the body by ingestion, inhalation or through the skin," Hrubec points out.
The level of quat exposure in humans has not been studied, she emphasizes. But it bears checking, especially as actually, we do eat them.
"Quats are used as preservatives on fresh fruits and vegetables, and have been detected in milk and other foods, so are ingested by humans," says Hrubec. "This study is on mice, but it showed that ambient air exposure is an important route of exposure. This is of concern because quats are widely used in settings where ambient exposure occurs."
The Israeli manufacturer Sano does not use such chemicals in its products, it stated in an email to Haaretz.