Children from birth to three years old who are exposed to fine particles from vehicle exhausts, industrial emissions and other sources of outdoor pollution are at greater risk of developing autism spectrum disorder (ASD) by up to 78 percent, according to a new study by Australian researchers from Monash University.
The research was conducted in Shanghai, China, and included 124 ASD children and 1,240 healthy children. The children were assessed in stages over a nine-year period, allowing the researchers to examine the association between air pollution and ASD.
The study, published in the journal Environment International, is the first to look at the effects of long-term exposure of air pollution on ASD during the early life of children in a developing country. The findings add to the body of growing evidence linking prenatal air pollution exposure to ASD in children.
“The causes of autism are complex and not fully understood, but environmental factors are increasingly recognized in addition to genetic and other factors,” said Associate Professor Yuming Guo from Monash University’s School of Public Health and Preventive Medicine in Australia.
“The developing brains of young children are more vulnerable to toxic exposures in the environment and several studies have suggested this could impact brain function and the immune system.”
“These effects could explain the strong link we found between exposure to air pollutants and ASD, but further research is needed to explore the associations between air pollution and mental health more broadly,” Guo said.
Air pollution is a major public health concern and is estimated to cause up to 4.2 million deaths each year worldwide, according to the World Health Organization (WHO). Outdoor pollutants contribute to a high burden of disease and premature deaths in countries including China and India, especially in densely populated areas.
Air pollution is rapidly becoming worse and there is no safe level of exposure, Guo said. Even in Australia where concentrations are typically lower, air pollution from burning fossil fuels and industrial processes leads to around 3,000 premature deaths a year — almost three times the national road toll and costing the economy up to $24 billion.
“The serious health effects of air pollution are well-documented, suggesting there is no safe level of exposure. Even exposure to very small amounts of fine particulate matter have been linked to preterm births, delayed learning and a range of serious health conditions, including heart disease,” Guo said.
The researchers investigated the health effects of three types of particulate matter: PM1, PM2.5, PM10. These are fine airborne particles that are the byproducts of emissions from factories, vehicular pollution, construction activities and road dust.
The smaller the airborne particles, the more capable they are of penetrating the lungs and entering the bloodstream causing a range of serious health conditions. PM1 is the smallest in particle size but few studies have been done on PM1 globally and agencies are yet to set safety standards for it.
“Despite the fact that smaller particles are more harmful, there is no global standard or policy for PM1 air pollution. Given that PM1 accounts for about 80% of PM2.5 pollution in China alone, further studies on its health effects and toxicology are needed to inform policymakers to develop standards for the control of PM1 air pollution in the future.”
Source: Monash University