Experimental PVC material challenge in subjects with occupational PVC exposure.

The incidence of asthma and allergy has increased during the past decades; this increase is considered to be caused by environmental exposure rather than genetic factors (Beasley et al. 2003; Selgrade et al. 2006). However, the mechanisms activated in exposed respiratory cells and tissues, as well as the causative particulate constituents and sources, remain to be clarified. In several epidemiologic studies the use of polyvinyl chloride (PVC) materials in indoor environments has been associated with an increased risk of asthma and allergy. It has been proposed that the plasticizer used in PVC carpets, diethylhexyl phthalate (DEHP), which binds onto the surface of building materials, may lead to the formation of substantial amounts of inhalable particles contaminated with agents of PVC origin (Oie et al. 1997). Recently, DEHP concentrations were found to be higher in buildings erected before 1960 (Bornehag et al. 2005a). This could reflect the higher fractional concentrations in older products or the higher emission rates as these products degrade. Thus, plastic building materials are potential chemical emission sources in indoor air. These emissions can cause inflammation and subsequently lead to an increased risk of asthma. This hypothesis is supported by studies on nasal, conjunctival, and asthmatic symptoms in relation to building dampness and the degradation of PVC flooring material (Norback et al. 2000; Wieslander et al.1999). These studies have shown that the degradation of DEHP from PVC flooring evokes conjunctival and nasal irritation and increases asthma-like symptoms in the exposed subjects. Furthermore, one PVC degradation product, 2-ethylhexanol, was detected in indoor air samples. Studies in young children have also revealed an association between the chemical emissions of PVC materials into indoor air and adverse respiratory effects (Jaakkola et al. 1999, 2000). In addition, Bornehag et al. (2004) reported that there was a dose–response relationship between asthma prevalence in children and the concentrations of DEHP in settled dust in their environments. The combination of water leakage and PVC as flooring material was also shown to be associated with a higher prevalence of airway, nasal, and dermal symptoms in exposed children (Bornehag et al. 2005b). Jaakkola et al. (1999) and Oie et al. (1997) proposed that phthalate esters act as either allergens or adjuvants; although there does seem to be a clear association between health problems and PVC materials, the etiologic factors behind this link are still unclear. In the present study, 10 subjects exposed to degrading PCV products at their workplace were challenged by PVC under controlled conditions. We have previously reported the renovation work being carried out in the building (Tuomainen et al. 2004).