Children living in areas with higher levels of small pollution particles and less green spaces might have up to 62 per cent increased risk of developing ADHD, according to a study. The research, published in the journal Environment International, found that children living in greener and less polluted areas have a 50 per cent lower risk of developing ADHD, one of the most prevalent neurodevelopmental disorders.
The researchers led by Matilda van den Bosch, from Barcelona Institute for Global Health (ISGlobal), used data from 37,000 children in Vancouver, Canada. They analysed the possible associations between exposure to greenness, small pollution particles (PM2.5) and noise in early life with later incidence of ADHD, which affects up to approximately 5-10 per cent children and adolescents. "We observed that children living in greener neighbourhoods with low air pollution had a substantially decreased risk of ADHD," said van den Bosch.
"This is an environmental inequality where, in turn, those children living in areas with higher pollution and less greenness face a disproportionally greater risk," she said. The study used administrative data of births from 2000 to 2001 and retrieved data on ADHD cases from hospital records, physician visits and prescriptions.
The percentage of green space in the participants’ neighbourhood was estimated with a novel and precise satellite metric, while the residential levels of two air pollutants -- NO2 and PM2.5 -- as well as noise levels were estimated using available exposure models. The possible associations between the three environmental exposures and ADHD were assessed using a statistical model that allowed to determine hazard ratios.
The researchers were able to identify 1,217 cases of ADHD, equivalent to a 4.2 per cent of the total study population. The green space analysis revealed that participants living in areas with a greater percentage of vegetation had a lower risk of ADHD, the researchers said. The results show that a 12 per cent increase in vegetation percentage was associated with a 10 per cent reduction in the risk of ADHD, they said.
The study found that participants with a higher exposure to fine particles had higher risk of ADHD. No associations were found for the rest of environmental exposures assessed: NO2 and noise, they said. The results are consistent with previous studies, which found associations between green space and air pollution, respectively, with ADHD. However, most of the research conducted until now focused on the evaluation of single exposures and rarely evaluated joint effects of multiple environmental exposures.
"These associations are particularly relevant because exposures take place in early life, a crucial period for brain development where children are especially vulnerable," van den Bosch said. "Our findings also show that the associations between PM2.5 and ADHD were attenuated by residential green space and vice versa, as if the beneficial effects of vegetation and the harmful effects of PM2.5 neutralised each other," said Weiran Yuchi, from the University of British Columbia, and first author of the study.
With PTI Inputs