Chlorine linked to Asthma

Conclusions: Regular attendance at chlorinated pools by young children is associated with an exposure dependent increase in lung epithelium permeability and increase in the risk of developing asthma, especially in association with other risk factors. We therefore postulate that the increasing exposure of children to chlorination products in indoor pools might be an important cause of the rising incidence of childhood asthma and allergic diseases in industrialised countries. Further epidemiological studies should be undertaken to test this hypothesis.

Lung hyperpermeability and asthma prevalence in schoolchildren: unexpected associations with the attendance at indoor chlorinated swimming pools

¹ Industrial Toxicology Unit, Faculty of Medicine, Catholic University of Louvain, B-1200 Brussels, Belgium
² Clinic of Allergology and Respiratory Diseases, St Pierre University Hospital, Free University of Brussels, rue Haute 322, B-1000 Brussels, Belgium
³ Departments of Human Physiology and Critical Care Medicine, School of Medicine, Flinders University, Adelaide, Australia

Correspondence to:
Dr A Bernard, Unit of Toxicology, Catholic University of Louvain, 30.54 Clos Chapelle-aux-Champs, B-1200 Brussels, Belgium;
bernard@toxi.ucl.ac.be

Aims: To study whether exposure to nitrogen trichloride in indoor chlorinated pools may affect the respiratory epithelium of children and increase the risk of some lung diseases such as asthma.

Methods: In 226 healthy children, serum surfactant associated proteins A and B (SP-A and SP-B), 16 kDa Clara cell protein (CC16), and IgE were measured. Lung specific proteins were measured in the serum of 16 children and 13 adults before and after exposure to NCl₃ in an indoor chlorinated pool. Relations between pool attendance and asthma prevalence were studied in 1881 children. Asthma was screened with the exercise induced bronchoconstriction test (EIB).

Results: Pool attendance was the most consistent predictor of lung epithelium permeability. A positive dose-effect relation was found with cumulated pool attendance and serum SP-A and SP-B. Serum IgE was unrelated to pool attendance, but correlated positively with lung hyperpermeability as assessed by serum SP-B. Changes in serum levels of lung proteins were reproduced in children and adults attending an indoor pool. Serum SP-A and SP-B were already significantly increased after one hour on the pool side without swimming. Positive EIB and total asthma prevalence were significantly correlated with cumulated pool attendance indices.

Conclusions: Regular attendance at chlorinated pools by young children is associated with an exposure dependent increase in lung epithelium permeability and increase in the risk of developing asthma, especially in association with other risk factors. We therefore postulate that the increasing exposure of children to chlorination products in indoor pools might be an important cause of the rising incidence of childhood asthma and allergic diseases in industrialised countries. Further epidemiological studies should be undertaken to test this hypothesis.

Keywords: chlorine; nitrogen trichloride; swimming; childhood asthma; lung epithelium permeability; pneumoproteins

Abbreviations: ANOVA, analysis of variance; BMI, body mass index; CC16, 16 kD Clara cell protein; EIB, exercise induced bronchoconstriction test; ETS, environmental tobacco smoke; PEF, peak expiratory flow; SP-A, surfactant associated protein A; SP-B, surfactant associated protein B

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