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4. Are certain people more vulnerable than others to indoor air pollution?

The SCHER opinion states:

3.1.2. Vulnerable groups

For the opinion, vulnerable groups are represented by children, pregnant women, elderly persons over 65 years of age, and persons suffering from asthma or other respiratory diseases, and cardiovascular diseases. For some pollutants (e.g. microbes) other health compromises (immunodeficiency) may render people more vulnerable. Genetic traits, nutritional status and life-style factors may also contribute (TNO and RIVM, 2006).

The assumption of different susceptibility of vulnerable groups (children, pregnant, elderly) to pollutants is based on age-dependent differences in physiology and toxicokinetics and varying responses due to existing diseases and genetic factors (e.g. IPCS 1993, Tamburlini et al., 2002, Pediatrics 2004).

Vulnerability to chemical toxicity after birth may be highest during the first 6 months (Scheuplein et al, 2002, Ginsberg et al., 2004) and continue for years before maturation. However, children may also be less sensitive and tolerate higher doses of chemical substances than adults, depending on the age and the compound (Schneider et al., 2002, Dourson et al., 2002). Higher exposure due to specific exposure patterns (e.g. hand-to-mouth activity in children) may increase the risk for children. Air pollutants may affect adversely foetal and infant lung development, cause post-neonatal infant mortality due to respiratory diseases, cause cough and bronchitis and aggravate asthma (WHO 2005b). The effect on lung function during development has been observed below the NOEL of effects of single air pollutants in adults, suggesting a higher susceptibility of children. The causative pollutants have not been identified but the association to adverse effects has been detected most consistently with outdoor particulate matter (PM), nitrogen dioxide and ozone (WHO 2005b). Studies addressing specifically the indoor environment, where the concentrations are different, are so far limited. Children’s higher susceptibility is known for lead and environmental tobacco smoke (Tamburlini et al., 2002, DiFranza et al., 2004); some concern has been expressed also for organophosphate pesticides (Grandjean and Landrigan, 2006, see also bullet 4a. in the opinion).

Altered physiology and toxicokinetics (e.g. reduced renal clearance) make elderly people potentially more sensitive (IPCS 1993) due to reduced capacity for elimination. However, elderly people may also be less sensitive to some effects (Kjaergaard et al. 1992, Shusterman et al., 2003) including nasal (Schusterman et al., 2003) and eye irritation (Kjaergaard et al., 1992) indicating that aging may also decrease the susceptibility.

People suffering from cardiovascular diseases are more vulnerable to particles (WHO 2003, Dominici et al., 2006) and persons suffering from asthma and other respiratory diseases are more susceptible to several air pollutants (WHO 2004a, 2005b). For example, sensory irritation may occur at lower exposure level in persons with allergic rhinitis (Shusterman et al., 2003, WHO 2005b).

Currently within Europe and other industrialized countries as well as international bodies, vulnerable groups are considered on a case-by-case basis in general. However, a major gap in identification of vulnerable groups is the lack of data, but several ongoing activities are attempting to extend e.g. reproductive toxicity testing to better address immunological and neurological differences. Additionally, physiological-based pharmacokinetic models can offer insight in intraindividual variability in pharmacokinetics (TNO and RIVM 2006).

The SCHER recommends that the science-based health risk assessment always addresses vulnerable groups; the impact on the evaluation should be based on a case-by-case approach, considering compound’s toxicological features and exposure. The SCHER also reminds that the Margin-of-Safety approach already includes specific safety factors to account for intraspecies differences.

Source & ©: SCHER,  Opinion on risk assessment on indoor air quality (2007),
3.1.2. Vulnerable groups, p. 11-12