German researchers say they have found some of the strongest evidence yet linking traffic pollution to childhood allergies¹.

The risk of developing asthma², hay fever, eczema or other allergies is about 50 percent higher for children living 50 meters (yards) from a busy road than for those living 1,000 meters away, they said in a study released on Friday.

Previous research has linked pollution to allergies, but to date observational studies in the field have been inconsistent, said Joachim Heinrich, an epidemiologist at the Helmholtz Research Centre for Environment and Health in Munich.

"We consistently found strong associations between the distance to the nearest main road and the allergic³ disease outcomes," Heinrich, who led the study, wrote in the American Journal of Respiratory and Critical Care Medicine.

The study followed 3,000 healthy children from all over Munich for six years from birth to determine rates of allergy-related diseases and exposure to traffic pollution.

The researchers mapped each residential⁴ address and the distance to busy roads, then developed a model to calculate exposure to pollution at birth and age two, three and six. A busy road was considered one used by 10,000 cars each day.

"We developed a model to predict air pollution concentration at one point in a metropolitan⁵ area," Heinrich said in a telephone interview.

This allowed the researchers to monitor more than one site as well as follow a large group of children over a long period of time, things many other studies did not do, Heinrich said.

The researchers will continue monitoring the children over the next few years to determine whether moving to a less-polluted area can reverse any of the traffic pollution-related problems, he added.