Air Quality Guidelines Global Update 2005 - World Health ...

DETERMINANTS OF SUSCEPTIBILITY
environmental agents, including particulate air pollution, as well as previous respiratory
infections. In one study, healthy nonsmoking volunteers 65–78 years of
age had increased neutrophils, immunoglobulin content and interleukin-6 levels
in bronchoalveolar lavage fluid compared to 20–36-year-olds (42). Thus, even
in the healthy elderly, years of exposure to external challenges may induce airway
inflammation and thereby increase susceptibility to a subsequent challenge.
Elderly individuals (60–80 years of age) without known coronary artery disease
experienced significant reductions in heart rate variability (HRV) with exposure
to concentrated ambient particles (43).
Children and infants also appear to be at increased risk, in part because they
exercise outdoors more than adults. Children are particularly susceptible to acute
respiratory infections, which are the most common cause of death in developing
countries. Evidence from a variety of studies suggests that exposure to air
pollution increases the risk of acute respiratory illnesses in children, including
pneumonia, and admission to hospital for respiratory illness (44). Pollutants implicated
include PM, sulfur dioxide, nitrogen dioxide and ozone. Proximity to
traffic appears to be a risk factor for respiratory symptoms and asthma in young
children (45).
One study (46) took advantage of the Mount St Helens eruption and demonstrated
that health effects are related to particle source. A total of 120 fourth-
and fifth-grade students in Montana underwent spirometry before and after
the Mount St Helens eruption in 1980. Peak levels of total suspended particles
reached astronomical levels in the days after the eruption, with a peak 24-hour
average of 11 054 μg/m 3 . There were no effects on pulmonary function associated
with these massive exposures to crustal-derived particles. However, when
the children were again tested several months later, when air particles were primarily
derived from urban pollution, a significant decline in the children’s lung
function was found in association with increased exposure to urban air particles.
More recent data have linked increased levels of air pollution with decreased
lung growth in individuals aged 10–18 years (47). High personal exposures to
fine particles may even be associated with adverse effects on the developing fetus
(48).
Nutrition
Many disorders involving inflammation share a potentially common mechanism:
tissue injury and activation from increases in reactive oxygen and nitrogen species.
These issues have been reviewed (49,50). Dietary intake of antioxidants has
been proposed as a protection against a variety of illnesses, including the health
effects of exposure to air pollution. Animal and human studies of ozone exposure
support the concept that antioxidant molecules in the epithelial lining fluid
of the lung react with inhaled ozone, serving as a protective barrier. For example,
ascorbate in epithelial lining fluid is consumed by exposure to ozone and
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