Children exposed to certain air pollutants in urban areas or some household chemicals are at higher risk of developing multiple sclerosis (MS) during childhood or adolescence, two new research studies suggest.
The studies “Urban air quality and associations with pediatric multiple sclerosis” and “Several household chemical exposures are associated with pediatric-onset multiple sclerosis” were published in the journal Annals of Clinical and Translational Neurology. They also were the focus of a news story by the National MS Society, which supported the research.
Although the cause of MS is unknown and no single risk factor is recognized for triggering the disease, increasing evidence points to the existence of several environmental and genetic factors contributing to the overall MS risk.
These recent studies on environmental risk factors suggest that exposure to specific air pollutants and common household chemicals increase the chance of children and teenagers developing pediatric-onset MS, whose first clinical attacks occur before the age of 18.
In the study addressing the effects of urban air quality, researchers conducted a case-control study in which they looked at 290 people who developed pediatric MS versus 442 controls without the disease. Researchers analyzed air pollutants in the participants’ county of residence, along with participants’ proximity to sites releasing industrial chemicals.
Prior exposure to air pollutants was tracked based on data from the Environmental Protection Agency (EPA).
Results showed that four pollutants (fine particulate matter, carbon monoxide, sulfur dioxide, and lead air emissions) were significantly associated with higher odds of having pediatric MS. These chemicals raised disease risk by 3.85- to 10.1-fold, depending on the pollutant and its concentration in the air.
However, these pollutants posed a significant risk only for participants who lived within 20 miles of an MS center, suggesting “the odds for MS increased in the more urban settings with increased levels of air pollution,” researchers wrote.
Although most study participants (75%) lived within five miles of a site releasing potentially harmful chemicals, people who developed pediatric-onset MS lived near sites that produced a higher load of air pollutants (81,000 tons), compared to sites close to healthy controls (35,000 tons).
“Particulate matter is created largely from combustion through industry and transportation sources,” researchers wrote, explaining that these particles could stimulate the immune response to mistarget the brain and spinal cord, or directly enter and cause damage to these tissues.
The second study focused on the effect of being exposed to common household chemicals and early MS onset.
Researchers asked the parents of 312 children with MS (median age 15.7, 63% girls) and 490 children without the disease (median age 15.0, 57% girls) about the exposure to chemicals such as synthetic fresheners, antibacterial soaps, pest control agents, weed control agents, and paint.
Results showed that people exposed anytime during childhood to rodent-killing agents, weed control products, and plant/tree insect or disease control products were at higher risk of developing pediatric MS. The risk was 1.99- to 2.72-fold higher than in those not exposed to these agents.
For both studies, further research is warranted to confirm that exposure to certain chemicals actually can cause pediatric MS and, if so, to determine why and identify the specific compounds contributing to that increased risk.
However, researchers also emphasized that research on environmental risk factors for MS should be interpreted with caution, because the combination of environmental and genetic factors are known to together contribute to MS risk.
These studies were made possible by the U.S. Network of Pediatric MS Centers, a nationwide cooperation between pediatric MS centers, launched and supported by the National MS Society, and whose mission is to uncover key pathogenic mechanisms underlying MS, and facilitate research to better understand the cause(s) of the disease, its features in children, and how best to treat children with MS.