Health Effects of Nitrogen Dioxide

Information on effects

Health Effects

Nitrogen dioxide is an irritant gas that has known effects on lung function and airway responsiveness. EPAQS have stated that studies have shown that it may also increase susceptibility to allergic responses. Healthy individuals show no effects at concentrations much higher than those found in the environment, however people with impaired lung function such as asthma sufferers are more susceptible. As a result those people with impaired lung function are likely to be affected by concentrations that can occur during pollution episodes. EPAQS have stated that there is no conclusive evidence to demonstrate the effect of long term exposure to nitrogen dioxide, although recent studies have shown that people who use gas cooking appliances in their homes showed more impaired function and less healthy lungs than those people who cooked with non-gas appliances.

Sources

Nitrogen dioxide (NO2) and Nitrogen oxide (NO) are both oxides of nitrogen and are collectively called NOX. All combustion processes in air produce NOX with NO being the prominent gas. The reaction of NO with oxygen can lead to the production of  NO2. The main sources of NOX are the burning of fossil fuels, power generation and from the emissions of petrol and diesel engines. In Hammersmith & Fulham the major source of NOX is from vehicular traffic which accounts for an estimated 76% of overall emissions. 

Standard

The standard to be achieved for Nitrogen dioxide has been set as an hourly average of 150 ppb and also as an annual average of 21 ppb.

Monitoring results

The Council has been monitoring Nitrogen dioxide for a number of years at sites across the borough (see Table 9). Currently seven sites are in operation. The sites are classified as either Roadside, Intermediate or Background depending on their proximity to busy roads. The 7 sites in the borough consist of 3 Roadside and 4 Background. The measured levels and annual concentrations are listed in Table 9. The figures listed in Table 9 represent annual average concentrations. No monitoring of hourly concentrations has been undertaken at the above sites. However, readings from the new air quality station installed at Hammersmith Broadway suggests that the concentrations of Nitrogen dioxide are currently in excess of the standard to be achieved by 2005.

Compliance with the standard

The NAQS states that a reduction of 48-62% (Chapter II.7) will be required in emissions from road traffic based on 1995 levels to allow compliance with the standard. At roadside locations this reduction may have to be as much as 70%. The strategy estimates that current policies should deliver a reduction of about 38%. Predicted increases in road traffic beyond 2010 however may increase overall Nitrogen dioxide levels. At present it is unclear how current policies will affect levels within the borough. Predicted reductions may be insufficient to achieve the standard set for 2005. It is therefore recommended that further assessment of Nitrogen dioxide take place to establish compliance with the NAQS standard.

Table 9 Average Annual Concentrations of Nitrogen Dioxide

  All figures in parts per billion
*indicates less than 6 months old

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