How to stop NOx from knocking

MANILA, Philippines - They say what you don’t know can’t kill you but in this case – they can’t be more wrong.

A joint report of the World Bank and the Department of Environment and Natural Resources (DENR) shows that air pollution causes 5,000 premature deaths each year in Manila. But images of blackened skylines and smoke-belching vehicles aside, do people really know enough about what’s killing them with every breath they take?

Here’s a closer look at nitrogen oxides (NOx), considered as one of the six primary air pollutants and one of the primary culprits of air pollution related fatalities:

Distinguishing marks

Nitrogen oxides (NOx) is the generic term for a group of reactive gasses containing nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless except for NO₂, which can be seen as a reddish-brown layer over many urban areas.

So how exactly is NOx formed? NOx forms when fuel is burned at high temperatures, for example, in a combustion process. Given this it’s not surprising that according to the US Environmental Protection Agency 49% of all emissions come from motor vehicles. Other NOx sources include electric utilities, fossil fuel combustion and even soil.

Its health and environmental impact has caught the attention of the scientific community and it is one of six principal air pollutants (along with carbon monoxide, lead, particulate matter, volatile organic compounds and sulfur dioxide) whose levels are monitored by the US Environmental Protection Agency (EPA). However, a US EPA report found that while levels of all the other air pollutants decreased significantly from the passing of the US Clean Air Act in 1970 to 1998, levels of NOx actually increased by 10% during this period.