According to the largest study of its kind, exposure to air pollution can lead to a higher severity of mental illness.
Research involving 13,000 Londoners found that an increase in nitrogen dioxide exposure led to a 32% rise in the likelihood of needing community-based care and an 18% rise in hospital admissions.
Researchers found that the findings could be applied to all cities in developed countries, with millions of people benefiting from reducing air pollution.
Joanne Newbury of the University of Bristol led the research. She said that air pollution can be controlled, on a large scale, as well as reducing exposure to the environment. There are many interventions that could be implemented, including expanding low-emission zones. Individual mental health interventions are quite challenging.
As a measure for severity, the study looked at hospital admissions and visits to community doctors. Researchers found that even a slight reduction in one pollutant could result in a decrease in illness and save the NHS millions of pounds per year.
Although levels of pollution have decreased in London in recent years, there is still a danger level. Ioannis Bakolis from Kings College London was part of the research team. This kind of important effect can be observed even at low levels.
Recent research shows that even small increases in pollution can lead to major rises in anxiety and depression. Research has shown that polluted air can lead to suicides, and can increase the likelihood of developing mental disorders. Another study has shown that pollution can cause a significant decline in intelligence, which is linked to dementia. In 2019, a global review concluded that air pollution could be affecting every organ of the body.
The British Journal of Psychiatry published a new study that tracked south London patients starting at the first contact with mental health services. It also used high-resolution air pollution estimates to determine their home.
The average quarterly NO2 levels in the area were between 18 and 95 micrograms per square metre (g/m). Researchers found that people who were exposed to higher levels of pollution (15g/m) had an 18% greater chance of being admitted to hospital, and a 32% greater likelihood of needing outpatient care after one year.
This link was strongest for NO2, which is mostly emitted from diesel vehicles. However, it was also significant for small particles pollution, which is caused by all fossil fuels. The levels of small particles ranged from 9 to 25 grams per meter. An increase in exposure of 3 units raised hospital admission risk by 11%, and outpatient treatment risk risk by 7%.
Seven years later, the scientists reexamined the patient data and discovered that the connection to air pollution is still evident. Although the findings could not be explained by other factors such as age, sex and ethnicity or density of population, it is possible that unidentified factors may still play an important part.
Researchers said that early intervention efforts could be aided by early identification of modifiable risk factors, such as relapse and severity. This would reduce suffering and the high economic costs associated with long-term mental illness.
This study did not attempt to establish a causal relationship between air pollution and mental illness. It requires hard experimental work. Researchers said that the link is biologically plausible because air pollutants have been shown to have powerful inflammatory properties. Inflammation is also believed to play a role in mood and psychotic disorders.
According to the World Bank, air pollution is estimated to cost the world's economy $5tn per year. This does not include the damage that can be done to the heart and lungs.
Newbury said that while cost evaluations are currently limited to physical health, there were increasing evidence linking mental health to costs. These could be important because they can tip the scales in favor of proving that investing in air pollution reduction is economically sound.
Researchers estimated that by reducing small particle pollution exposure by just a few units in the UK, to the World Health Organizations annual limit at 10g/m, the UK's urban population would be able to reduce its use of mental health services by around 2%, and potentially save tens to millions of pounds annually.
Professor Kevin McConway from the Open University, who wasn't part of the study team said that it was a great study. The statistical analysis is generally valid and does increase confidence in the existence of some cause and effect in relation to pollution and mental illness.
It is not easy to reduce pollution. It is necessary to take broad-based, communal action to reduce air pollution in cities.
Another study found that heart attacks increase with increasing levels of air pollution. The study examined data from southern Lombardy, Italy, which has 1.5 million people.
Francesca Gentile of the IRCCS Policlinico San Matteo Foundation, Pavia said: These results could be used [and] improved health service efficiency by being factored in to ambulance forecasting models.
