RISK FACTORS
There is a complex interaction between the building environment, infectious agents, allergens, occupational exposures, school environment and recreational exposures, which contribute to shape the exposome3.
The amount and impact of CBPs exposure may be influenced by the dose of disinfectant, the resultant concentration of CBPs in the water and the air, the number of attending swimmers, temperature of water and air, ventilation rates in the building, duration of swimming, and the water turbulence2,87. The three routes of exposure (inhalation, ingestion and dermal absorption) vary for different age groups and are affected by several factors (Figure 2 ). Some conditions related to competitive swimmers are highlighted intable 3 .
Inhalation – Swimming-pool attendants inhale from the atmosphere just above the water’s surface, and the volume of air inhaled is a function of the effort intensity and time. In indoor swimming-pools, individuals also breathe air in the wider area of the building housing the pool. A correlation between physical activity and THM concentrations88 has been identified.
Ingestion – Inadvertent water intake in the swimming-pool varies according to age and sex, with adult women ingesting the least and male children ingesting the most, especially babies.
Dermal/mucosal absorption - Chlorination of bathing water showed to change the dermal barrier function, especially of atopic skin89, the same being expected for chlorination of the swimming-pool water. Infant swimming practice combined with atopy has been shown to increase the prevalence of eczema90.
Age seems to be the most relevant personal risk factor for respiratory and reproductive health effects of CBPs exposure in swimming pools. The first years of life may be seen as a “window of sensitivity” given the progressive increase in maturation of respiratory tract and reproductive system.
Age also directly impacts the other risk factors, including the surface areas of both the head and the body, the breathing rate and body weight2. The contribution from each exposure route changes dramatically for each age group, and the time spent swimming must also be taken into consideration. Adjusted for body weight, the uptake of CBPs by all routes is clearly higher in infants or children and decreases with age. A schematic representation is presented infigure 3 .
As previously mentioned, the use of indoor chlorinated-pools especially by young children interacts with atopic status to promote the development of childhood asthma52, and a synergistic action of exposure to pets and environmental tobacco smoke in chlorinated-pools attendants predisposes to the development of asthma51.