Air Pollution Nitrogen Dioxide
3. How are we exposed to Nitrogen Dioxide (NO2)?
- 3.1 Which are the critical sources of NO2 responsible for health effects?
- 3.2 What is the relationship between ambient levels and personal exposure to NO2?
- 3.3 What is the health relevance and importance of short-term exposure to high peak levels or exposure in hot spots for NO2?
3.1 Which are the critical sources of NO2 responsible for health effects?
WHO states: "In
most urban environments in Europe, the principal source of
NO2 is NOx from motor vehicles of all
types and energy production in some places [e.g., power plants,
Source & ©: WHO Europe (2003)
The map below illustrates regions where traffic and fuel combustion contribute to NO2 air pollution. It shows the mean ground level nitrogen dioxide (NO2) concentration between January 2003 and June 2004, as measured by Satelite.
Source: European Space Agency www.esa.int/esaCP/ Credits: University of Heidelberg
The same information on
3.2 What is the relationship between ambient levels and personal exposure to NO2?
Can the differences influence the results of studies?
WHO states: "In
any particular setting the answer will depend on the relative
contributions of outdoor and indoor sources and on personal
activity patterns. A direct relationship between personal
exposure and outdoor
concentrations is found in
the absence of exposure to indoor sources such as unvented
cooking or heating appliances using gas, and tobacco smoking.
However, since outdoor NO2 is subject to wide
variations caused by differences in proximity to road traffic
and local weather conditions, the relationship of personal
exposure to measurements made at outdoor monitoring stations is
variable. Results of epidemiological studies relying on outdoor
NO2 concentrations may be difficult to interpret if
account is not taken of exposure to indoor sources."
3.3 What is the health relevance and importance of short-term exposure to high peak levels or exposure in hot spots for NO2?
Adverse health effects
have been documented after short-term
exposure to peaks, as well as
after long-term exposure to relatively low
NO2. Experimental studies indicate that short-term
exposure to high concentrations of NO2 increases
exposure over time has also been linked to mortality and disease
progression. A direct comparison of the health relevance of
short term and long-term
exposures has not been
reported for NO2.
Some studies have documented that subjects living close to
busy roads experience more short- term and long-term effects of
air pollution than subjects living further away. In urban areas,
up to 10% of the population may be living at such
“hot spots”. The public
health burden of such
exposures is therefore
significant. Unequal distribution of health risks over the
population also raises concerns of environmental justice and