New research from Germany has found a link between traffic pollution and childhood allergies.
A study by researchers from the Helmholtz Research Centre for Environment and Health in Munich has produced some of the strongest evidence to date which links traffic pollution to children's allergies.
The researchers say that risk may be as much as 50% higher for children living near a busy road.
There has always been the suspicion that pollution and allergies are linked but this latest research has found strong associations between the distance to the nearest main road and the allergic disease outcomes.
Epidemiologist Joachim Heinrich, who led the study, says the risk of developing asthma, hay fever, eczema or other allergies is about 50 percent higher for children living 50 metres from a busy road than for those living 1,000 meters away.
While other research has linked pollution to allergies, observational studies have been inconsistent.
This study followed 3,000 healthy children from across Munich from birth, over six years, to determine the rates of allergy-related diseases and exposure to traffic pollution.
In order to develop a model with which to calculate exposure to pollution at birth and age two, three and six, the researchers mapped each residential address and the distance to busy roads - a busy road was defined as one used by 10,000 cars each day.
The model enabled the researchers to predict air pollution concentration at one point in a metropolitan area and allowed them to monitor more than one site as well as follow a large group of children over a long period of time.
Heinrich says they will continue monitoring the children over the next few years to determine whether moving to a less-polluted area reverses any of the traffic pollution-related problems.
The findings are published in the American Journal of Respiratory and Critical Care Medicine.