Urban air quality is a significant cause of death and illness. There is a statistically significant relationship between higher levels of fine particles and respiratory and cardiovascular disease, and increased mortality. In 2013, the International Agency for Research on Cancer classified outdoor air pollution as a human carcinogen. There is clear evidence that even short periods of poor urban air quality have serious adverse impacts on human health.
A limitation of the standards-based approach is that there is now strong evidence that many pollutants do not have a recognised threshold below which there are no adverse health effects. Thus, the 2016 update of the Air NEPM includes a new requirement to report on a population exposure metric for fine particulate matter (PM2.5) each year, starting in 2018. This will provide data to assess changes in population exposure and better target control measures.