New research at Ohio State University in the US has revealed that childhood exposure to common air pollutants increases the risk of obesity and developing diabetes.
Exposure to microscopic pollutants from car exhausts and burning fossil fuels can lead to weight gain in youngsters brought up in cities, say researchers, reports the Daily Express.
They also discovered that the pollutants cause increased insulin resistance, which can lead to the development of Type 2 diabetes.
The results are based on tests on mice and the pollution levels they were exposed to matched the levels found in urban areas.
One group of baby mice was exposed to microscopic pollution particles and another breathed filtered air.
Their ages matched toddlers to late adolescent humans and mice from both groups were fed a normal diet or a high-fat diet.
All the animals on a high-fat diet gained extra weight but the mice on a normal diet who were exposed to the atmospheric pollutants for six hours a day over 10 weeks saw elevated levels of blood sugar.
They also had higher levels of insulin resistance, as well having higher levels of fat both around their abdomen and internal organs.
Mice on a high-fat diet who breathed in the airborne toxins did not gain any more weight than their counterparts on a high-fat diet, who were breathing fresh air.
But mice exposed to pollutants while on a normal diet did have increasing levels of body fat, suggesting that exposure to pollutants was enough to trigger weigh gain.
The study was led by Dr Qinghua Sun, the university`s associate professor of environmental health sciences.
The study has been published in the journal Arteriosclerosis, Thrombosis and Vascular Biology.