Researchers in Germany have linked air traffic pollution to increased insulin resistance in children as young as 10 years of age. In fact, living close to a major highway raises resistance by 7 percent every 500m, researchers say.
Several studies have previously documented the adverse effects of exposure to air pollution: increased risk of cardiopulmonary morbidity, acute cardiovascular ailments and even death. Exposure to chronic traffic and air pollution specifically raises the risk of atherosclerosis by increasing oxidative stress and low-grade inflammation in the endothelial cells and macrophages. The same biological mechanisms also mediate the pathogenesis of type 2 diabetes mellitus, due to impaired insulin resistance.
In the first prospective study that investigated the impact of long-term traffic-related air pollution on children, researchers in Germany show that insulin resistance levels increased with increasing traffic-related air pollution exposure.
"Although toxicity differs between air pollutants, they are all considered potent oxidisers that act either directly on lipids and proteins, or indirectly through the activation of intracellular oxidant pathways," explains one of the lead researchers, Joachim Heinrich, in a recent interview with BBC.
In the study published in the journal Diabetologia, Elisabeth Thiering and Joachim Heinrich of the German Research Centre for Environmental Health in Neuherberg, looked into 397 10-year-old children living close to a major road. After sampling their blood at the age of 10 for glucose and insulin levels, the researchers estimated their degree of exposure to air pollution, using figures from 2008-09 for their birth address neighborhood, after adjusting for birth weight, body mass index (BMI) and exposure to second-hand smoke at home.
The findings suggest that children with higher exposure to air pollution, such as nitrogen dioxide and fine particulate matter, showed increased levels of insulin resistance, and more so if they had higher BMIs. It is known that air pollutants can oxidize lipids and proteins in the blood, and thereby adversely affect health. Indeed, several previous studies have shown the dreadful effects of air pollution in terms of other chronic conditions, such as atherosclerosis and heart disease.
"Oxidative stress caused by exposure to air pollutants may therefore play a role in the development of insulin resistance," commented Prof. Frank Kelly of King's College London, in his interview with BBC.
However, the reasons may not be so well established. "As the authors point out, their measurements of fasting blood insulin levels and estimations of air pollution levels were not taken at the same time.Therefore, these results should be regarded with caution, and a larger and methodologically more secure study needs to be done to confirm the possible link between air pollution from traffic emissions and insulin resistance in children," says Prof. Jon Ayres, an expert in environmental and respiratory medicine, of the University of Birmingham, according to the BBC news.
Nonetheless, it is plausible that children are susceptible to the air pollution more than adults.
"They have a larger lung-to-body volume ratio, their airway epithelium is more permeable to air pollutants, and the lung defence mechanisms against particulate matter pollution and gaseous pollution are not fully evolved," according to Kelly. "Breathing the same pollutant concentrations, children may have a two to fourfold higher dose reaching the lung compared with adults.
"Given the ubiquitous nature of air pollution and the high incidence of insulin resistance in the general population, the associations examined here may have potentially important public health effects despite the small/moderate effect sizes observed," the researchers conclude in their published report.
