The incidence of asthma has risen significantly over the last 25 years. This short time span suggests that some change in the environment is responsible and recent studies have indicated that exposure to organophosphates at low environmentally-relevant concentrations may at least be partly responsible.

Airway tone is achieved by a balance between the contradictory
action of two sets of nerves, one of which sends a signal to the muscles around the airway to contract, and the other sends a message to relax. Organophosphates inhibit one of these sets, the set responsible for relaxing the muscles, causing overconstriction of the airways.

Sensitisation to a particular allergen in the environment is a significant factor contributing to asthma.
Researchers looked to see whether sensitisation to an allergen would have an impact on the effect of organophosphates (parathion in particular) on asthma. They found that allergen sensitisation makes the airway more vulnerable to organophosphates.
As half of the general population, and four out of five asthmatics are sensitive to an allergen, these findings have significant implications for organophosphate risk assessment.

Ref: Proskocil BJ, Bruun DA, Lorton JK, Blensky C, Jacoby DB, Leis PJ and Fryer AD, Antigen sensitisation influences organophosphorus pesticide-induced airway hyperreactivity. Environmental Health Perspectives, 2008, 116 (3) 381–388.

Courtesy of PAN UK
www.pan-uk.org 020 7065 0905

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First Publishd in August 2008

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