In some neighbourhoods, 19 per cent — nearly 1 in 5 — of children have asthma, while in others the rate can be as low as 3 per cent. Heavy traffic, industrial incinerators, and other outdoor air pollution sources have all been blamed in the past.
But researchers at Columbia University have now found that children living in neighbourhoods with high rates of asthma were twice as likely to carry antibodies against a cockroach protein in their blood, a sign the children had been exposed to the insects and were likely allergic to them.
In addition, homes in the neighbourhoods with high rates of asthma contained more of the allergen produced by cockroaches in household dust.