London School of Hygiene & Tropical Medicine

In 2015, around 4.5 million people died prematurely from diseases attributed to ambient outdoor air pollution - including 237,000 children under the age of five from respiratory infections, according to a new study published in The Lancet Planetary Health.

The research, co-authored by the London School of Hygiene & Tropical Medicine (LSHTM) and led by the Max Planck Institute for Chemistry, estimated excess deaths attributable to ambient air pollution by disease category and age group, using a global model of atmospheric chemistry.  They calculated that in 2015 about 270,000 excess deaths occurred from exposure to ozone and 4.28 million from particulate matter.

The causes of death attributed to ambient air pollution included lower respiratory tract infections (727,000 deaths ), chronic obstructive pulmonary disease (COPD – 1.09 million deaths), cerebrovascular disease (920,000 deaths), heart disease (1.5 million deaths) and lung cancer (304,000 deaths). As a result of these excess deaths, approximately 122 million years of life were lost worldwide in 2015. The authors say these figures are likely to be conservative estimates because other diseases which may also be related to air pollution have not been taken into account.

According to the World Health Organization (WHO), around one million children younger than five years old died from lower respiratory infections in 2015. Fine particulates smaller than 2.5 microns in diameter (PM2.5) play a decisive role. Fine particulates penetrate deeply into the respiratory tract, and as a result can increase the risks of respiratory infections, ischaemic heart disease (heart attacks), COPD, cerebrovascular disease (strokes) and lung cancer.

Between 2000 and 2015 the global average concentration of fine particulate matter which people were exposed to has increased from around 40 to 44.0 micrograms per cubic meter of air. This is more than four times the concentration of 10 micrograms recommended by the WHO as an upper limit for annual mean exposure.

The irritant gas ozone also contributes to respiratory health effects. The origin of particulate matter differs from country to country. In India for example, the burning of solid fuels for cooking and heating is the most important single source, whereas power plants, transport and agriculture are the largest sources in the United States of America. The air inside buildings from household pollution can also pose a major health risk.

This study focused on children under the age of five who may be particularly sensitive to the effects of air pollution on respiratory infections. The calculations showed that in 2015, out of a total of 669 million children under five around the world, about 240,000 died from poor air quality as a result of lower respiratory tract infections, particularly pneumonia. In comparison, 87,000 children died from HIV/AIDS, 525,000 from diarrhoea and 312,000 from malaria in the same year.

The likelihood of children dying from polluted air was particularly high in sub-Saharan Africa. In low-income countries, potentially curable diseases are often fatal because many children are undernourished and medical care is inadequate.

In Chad for example, the health risk for children from ambient air pollution is almost ten times higher than the global average, substantially reducing life expectancy. In sub-Saharan Africa, children lose four to five years of life expectancy on average due to ambient air pollution.

The study also shows that in some lower middle-income countries, notably India and Pakistan, the mortality rate for girls is 1.2 times higher than for boys, which may reflect differences in nutrition and health care. On the other hand, the study shows that in India child mortality due to air pollution is declining, probably because health care, household air pollution and nutrition are improving. Nevertheless, as ambient air quality continues to deteriorate, the cause of mortality shifts to other diseases and older people.

Sir Andy Haines, co-author and Professor of Environmental Change and Public Health at LSHTM, said: “By combining estimates of air pollution concentrations and disease occurrence globally, we’ve been able to quantify the effect of air pollution on health outcomes, showing that this is an important contributor to excess mortality, including in children under five.

“Although the proportion of deaths from air pollution varies across the world, rates are higher in low and lower-middle income countries, as high levels of exposure are often coupled with poor nutrition and inadequate health care.’

“Reducing air pollution, improving  nutrition and providing effective  treatment for the pollution-related  health outcomes , such as lower respiratory tract infections, will be essential in reducing these excess deaths particularly in  low and lower middle-income countries in Africa and Asia.”

The study was funded by the Max Planck Institute for Chemistry.

Publication

Jos Lelieveld, Andy Haines, Andrea Pozzer. Age-dependent health risk from ambient air pollution: a modelling and data analysis of childhood mortality in middle-income and low-income countries. The Lancet Planetary Health. DOI:10.1016/S2542-5196(18)30147-5