Chlorination Products: Emerging Links with Allergic Diseases

Abstract

Exposure of the human population to chlorination products has considerably increased during the 20(th) century especially after the 1960s with the development of public and leisure pools. The present article summarizes current knowledge regarding the human exposure to chlorination products and reviews studies suggesting that these chemicals might be involved in the development or exacerbation of allergic diseases. Populations regularly in contact with chlorination products such as swimmers, lifeguards or workers using chlorine as cleaning or bleaching agent show increased risks of allergic diseases or of respiratory disorders frequently associated with allergy. Experimental evidence suggests that chlorination products promote allergic sensitization by compromising the permeability or the immunoregulatory function of epithelial barriers. These findings led to the chlorine hypothesis proposing that the rise of allergic diseases could result less from the declining exposure to microbial agents (the hygiene hypothesis) than from the increasing and largely uncontrolled exposure to products of chlorination, the most widely used method to achieve hygiene in the developed world. Giving the increasing popularity of water recreational areas, there is an obvious need to assess the effects of chlorine-based oxidants on human health and their possible implication in the epidemic of allergic diseases.

Swimming pool, respiratory health, and childhood asthma: Should we change our beliefs?

“…Chlorine as a disinfectant has two drawbacks, however: (1) it is a non-specific biocide and when used in drinking or swimming pool water, its concentration must be carefully controlled; (2) when added to swimming pool water, chlorine transforms organic contaminants into a mixture of potentially harmful products, that can be absorbed by inhalation, ingestion and absorption through the skin. 3 In fact, chemicals found in pool water include the disinfectants themselves and the disinfection byproducts (DPB) produced by chemical reactions with organic and inorganic material. 8,9 The reaction of hypochlorite with ammonia and amino-compounds derived from the swimmers' urine, sweat, and skin particles generate inorganic chloramines (monochloramine, dichloramine, and trichloramine), which are mainly responsible for the smell and irritant properties of swimming pool air (Fig.…”

“…It is worth remembering that air chloramine concentration is higher in indoor pools than in outdoor pools. 3 The levels of free chlorine currently considered acceptable to achieve adequate disinfection vary widely around the world, with 0.3-0.6 mg/L in Germany, 0.6-1.2 mg/L in Italy, 1-2 mg/L in the United Kingdom, and 1-3 mg/L in the USA. 8 It is recommended that acceptable levels of free chlorine continue to be established at local level, but in public pools these should not exceed 3 mg/L and in public/semi-public hot tubs they should not exceed 5 mg/L.…”

“…In the light of recent studies, a new hypothesis named ''pool chlorine hypothesis'' 1,2 has been postulated, that is that increasing exposure to the harmful by-products of chlorination (the most commonlyused method for ensuring water hygiene in swimming pools), might have a role in the rising numbers of children with asthma, and allergy in industrialized countries. 1,3 As well as tobacco smoke and other environmental irritants, chlorine and its by-products might therefore have a role in causing and/or triggering asthma.…”

Asma e natação: pesando os benefícios e os riscos

“…The current hypothesis is that these chemicals irritate the airways of swimmers and thereby make them more sensitive to environmental stressors such as allergens or infection agents. 6 This interpretation is supported by biomarker studies showing that chlorination products can cause acute or chronic disruption of the lung epithelial barriers. 7,8 Ironically, and adding to the confusion, the physicians who first alerted the medical community about the risks of pool chlorine had their attention drawn by the effects of these chemicals on the airways of their asthmatic patients.…”

Ocorrência de sintomas asmáticos e de distúrbio obstrutivo em nadadores amadores de 8 a 17 anos de idade

“…(2)(3)(4)(5)(6) Although the underlying mechanisms responsible for developing asthma symptoms during swimming are still unclear, exposure to irritants, such as the chlorine compounds that are used in order to disinfect swimming pools, have been found to play a role in airway inflammation and therefore to predispose to bronchoconstriction. (7)(8)(9) While practicing their sport, swimmers inhale large amounts of air from just above the surface of the water, as well as being susceptible to the microaspiration of water into their trachea and bronchi. (7) Children and adolescents who swim constitute a relevant epidemiological population to be investigated, not only because of chlorine exposure and its risks, but also because they have a higher prevalence of asthma symptoms than do adults.…”