Indian students cover their faces as they walk to school amid heavy smog in New Delhi on November 8, 2017.

Indian students cover their faces as they walk to school amid heavy smog in New Delhi on November 8, 2017.

(Photo: Sajjad Hussain/AFP via Getty Images)

New Report Details Harmful Impact of Air Pollution at Every Stage of Life

"Controlling emissions will provide the greatest benefit to all," says an assessment of recently published research.

Air pollution negatively affects every stage of human life, from impairing fetal development and physical as well as intellectual growth during childhood to accelerating bodily and cognitive decline in adulthood.

That's according to a new report, released Monday by the Environmental Research Group at Imperial College London (ICL), which synthesizes the findings of more than 35,000 studies on the connections between air pollution and ill health published over the past decade by scientists from around the globe.

The review of research from the World Health Organization (WHO), the International Agency for Research on Cancer, and other institutions puts an emphasis on investigations "carried out in the United Kingdom, London, or cities with similar air pollution climates."

"Numerous studies across Europe, including several conducted in London, have shown direct impacts of contemporary air pollution in our city," says the report. "These include evidence that air pollution exposure is having impacts during pregnancy and affecting birth outcomes, that school children are experiencing slower lung development, worsening of asthma symptoms, and poorer mental health, and that Londoners are suffering more disease in later life and dying earlier because of the air they breathe."

"While headline figures on the health impact of air pollution focus on the equivalent number of premature deaths, the wider impacts are hiding in plain sight in the contribution of air pollution to the burden of chronic diseases."

"While headline figures on the health impact of air pollution focus on the equivalent number of premature deaths, the wider impacts are hiding in plain sight in the contribution of air pollution to the burden of chronic diseases," the report continues. "These affect our quality of life and have a large cost to society through additional health and social care costs, as well our ability to learn, work, and contribute to society."

"Perhaps the most important new finding is evidence related to both the impact of air pollution on brain health, including mental health and dementia, and early life impacts that could lead to future health burdens within the population," it adds. "Both represent significant but currently unquantified costs to society and the economy."

ICL's analysis of studies published since 2012 details how air pollution, which WHO describes as a global public health emergency, harms people from conception to old age.

"Each breath we take contains a complex mixture of pollutants.," the report notes. "It can therefore be difficult to separate out the individual impacts of these multiple components. However, it is clear that a substantial part of the health burden from air pollution comes from small respirable particles, most especially those referred to as PM2.5, and also from the gas, nitrogen dioxide."

The report summarizes adverse outcomes across the life course.

Pregnancy and birth outcomes

Maternal exposure to air pollution during pregnancy is associated with slower fetal growth rates and increased probability of low birth weight and preterm birth, which are "established risk factors for early life mortality and lifetime morbidity," the report points out. "It has been estimated that 2.8 million low-weight births and 5.9 million pre-term births could [have been] avoided globally [in 2019] if PM2.5 exposure during pregnancy was maintained at the theoretical minimum risk exposure levels."

The negative impacts of air pollution on reproductive health are not limited to expectant mothers, as recent research highlights adverse effects on semen volume along with sperm concentration and mobility.

The developing child: from birth through adolescence

Following birth, "childhood and adolescence are periods of rapid growth during which organ systems are particularly susceptible to developmental impairment and damage," states the report. "These earlier life impacts are increasingly understood to have lifelong consequences on an individual's vulnerability to chronic disease as they age."

There is mounting evidence that exposure to air pollution hinders children's lung growth. A study on primary school-aged children in inner-city London, for example, found that "on average a child had lost around 5% of their expected lung volume because of the air pollution that they breathed," the report says. "This effect was most clearly linked with exposure to NO2, which is often used as a tracer for... diesel exhaust emissions."

"Adverse health effects have also been seen in relatively low pollution environments, far below those experienced in London," the report continues, but "there is evidence that policies to reduce air pollution can deliver measurable health benefits."

Childhood exposure to polluted air has also been proven to exacerbate asthma, and other research suggests that it could increase blood pressure and decrease cardiovascular function. Moreover, traffic-related air pollution exposure is correlated with lower cognitive abilities, more behavioral issues including inattention and hyperactivity, and higher risk of depression.


Research has long shown that adults residing in more polluted places live shorter lives and that their lifespans decrease in relation to the amount of local PM2.5. Relatedly, ICL's review of recent studies notes that people living in highly polluted areas are "more likely to be living with more than one long-term illness."

Exposure to air pollution is associated with deteriorated cardiac health and increased rates of heart disease, hospitalization, and death. In addition, there is "increasingly compelling evidence" that air pollution exposure increases the risk of stroke and ensuing hospitalization and mortality, says the report. Long-term exposure to traffic-related air pollution has also been linked to adult-onset asthma and other respiratory problems.

Furthermore, diesel exhaust, outdoor air pollution, and airborne particulate matter have been classified as human carcinogens, with researchers especially concerned about the development of lung cancer, including in people who have never smoked.

"One of the most significant recent developments in our knowledge of the way that air pollution may be affecting our health," the report states, is growing confidence about "the associations between air pollution, mental health, cognitive decline, and dementia."

Policy implications

"Actions and policies to reduce the concentrations of air pollution are often framed in terms of meeting legal limit values to minimize the harm to human health," the report points out. "These limits should not be perceived, or presented as 'safe,' non-toxic thresholds."

"Abundant evidence suggests significant impacts below these concentrations, and for some pollutants, such as PM2.5 there is no evidence to identify a threshold where exposure does no harm," the report continues. "The latest evidence, reflected by the new WHO guideline concentrations for PM2.5 and nitrogen dioxide, suggest that current levels of air pollution in London will affect all citizens, including those living in the least polluted suburbs, and especially those with pre-existing vulnerabilities."

The authors emphasize that "controlling emissions will provide the greatest benefit to all, but actions are required at all levels of government and healthcare to also educate about the risks of air pollution and provide advice to reduce exposures in the shorter term, through actions such as behavior change."

Last year, the Lancet Countdown found that moving toward "sustainable energy, transportation, waste management, and agricultural systems could help prevent the 3.3 million deaths attributable to anthropogenic PM2.5 in 2020, including the 1.2 million directly related to the combustion of fossil fuels."

As ICL's assessment of recent research warns: "The focus on achieving current limits can lead to actions on the most polluted places but provides little incentive to drive down air pollution in other locations. It can also be a barrier to progress when limits are set according to their achievability in the most polluted places."

"For PM2.5, European and U.K. legislation includes targets to reduce the average exposure across the whole population, but there is also an urgent need to incorporate population vulnerability in air pollution priorities," the report stresses. "Policies should be aimed at reducing the accumulating harm from air pollution and the health degradation, in addition to protecting people who have become vulnerable to current pollution concentrations."

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