By Nancy Maes
Pesticides seem necessary to keep the home free from ants, cockroaches and other insects, but the toxic chemicals may do more harm than good. A recent study published in the journal Pediatrics reports that youngsters exposed to a chronic, low level of residential insecticides may have an increased risk of developing childhood blood cancers. Researchers analyzed the results of 16 previous studies published between 1993 and 2012, concluding that children exposed to pesticides in the home had a 47 percent increased risk of developing leukemia and a 43 percent increased risk of developing lymphoma.
Although the rates of childhood cancers are low, the number of cases is going up. More than 3,000 cases of acute lymphoblastic leukemia, the most common cancer in children and adolescents, and more than 1,000 cases of childhood non-Hodgkins lymphoma are diagnosed in the United States each year, according to CureSearch for Children’s Cancer.
“The rates of these cancers are on the rise, and we don’t know why,” says Jennifer McNeer, MD, a pediatric oncologist at the University of Chicago Comer Children’s Hospital. “The development of a cancer is very complex and is probably due to a combination of genetic risks as well as environmental exposures. So, if you have someone who is not genetically inclined to developing cancer, something like insecticides will not necessarily cause cancer. But perhaps for children who for one reason or another have a genetic predisposition, exposure might trigger the development of the cancer.”
The authors of the Pediatrics study suggest that children may increase their exposure to pesticides when they play on the floor, where they may touch areas treated with pesticides and then put their hands in their mouths. It’s a speculation though, says Charles Hemenway, MD, a pediatric oncologist at Loyola University Medical Center. “This is an epidemiological study, so it basically looks at the statistical associations between pesticide exposure and childhood cancers without trying to identify the causalities,” he says.
The authors of the study point out that children may be more vulnerable to the hazards of pesticides because their immune systems are immature, so they may not be able to detoxify and excrete pesticides as well as adults. But Hemenway sees a different link between a child’s immune system and cancer.
“I think there is pretty good agreement, based on scientific evidence, that for certain types of childhood leukemia, the immune system is rapidly developing, and the maturation of the immune system involves the rearrangement of certain genes inside of cells called lymphocytes. If that process goes just slightly wrong, you could have a genetic abnormality that drives the risk,” he says. “How pesticides would exacerbate that I personally don’t know, and I’m not sure anyone knows.”
Some causes of leukemia have been firmly documented, Hemenway says, such as exposure to excessive radiation in the Chernobyl nuclear plant accident and the explosion of the atomic bomb. In addition, children with Down syndrome, which occurs when a person has all or part of a third copy of chromosome 21, also have an increased risk of leukemia. “A lot of work is being done to understand that connection, which might help us to identify certain genes, especially on the 21st chromosome, that contribute to leukemia,” Hemenway says.
Authors of the meta-analysis point out that more research needs to be done on the link between childhood cancers and pesticides. They also recommend that every effort be made to limit children’s exposure to the toxic chemicals of pesticides.
“Pesticides are never safe,” says Ruth Kerzee, executive director of the Chicago-based Midwest Pesticide Action Group, which works to reduce the health risks and environmental impact of pesticides. “When you bring pesticides into your home, you bring in poisons that are designed to kill.”
Pests need food, water and a hiding place, so it’s crucial to eliminate these essentials in order to keep the home pest free, she says. If it is still necessary to use pesticides, she suggests using contained baits, rather than sprays, to limit children’s exposure. Boric acid, amorphous silica gel and diatomaceous earth are other safer pest-control options.
“We are exposed to a lot of different pesticides, so it’s hard to tease out which ones are causing what problems,” Kerzee says, “but we see a lot more pediatric associations publishing articles that recommend that children avoid exposure to [even] the very lowest levels of pesticides because we are seeing indications that they are causing problems.”
Originally published June 30, 2016