How air pollution raises risk of early death, by study

*Phenomenon associated with mental disorders, depression, anxiety
*Noxious gases interfere with brain turning people into violent offenders
*Long-term exposure doubles chance of developing age-related blindness

Exposure to even the lowest amounts of pollution raises the risk of an early death, scientists have said following major research.

In the world’s largest ever study of toxic air, researchers analysed levels of pollution in 652 cities across 24 countries and regions.

Scientists found when levels of pollution spike, so does the number of deaths, including those from heart failure, asthma and lung diseases.

More than 25million people died from cardiovascular or respiratory diseases over the 30-year study period, including 1.2million in the United Kingdom (UK) and 14.4million in the United States (US).

Tiny particles, called particulate matter (PM) can be inhaled deep into the lungs where they irritate the lining and enter the bloodstream. There is no ‘safe’ level of exposure, scientists said, suggesting current air quality guidelines don’t protect public health.

It comes after three damning scientific papers published yesterday warned pollution also raises the risk of depression, bipolar disorder and blindness.

A co-author of the study from Monash University in Australia, Prof. Yuming Guo, said: “There’s no threshold for the association between particulate matter (PM) and mortality. Even low levels of air pollution can increase the risk of death.”

The study, published in the New England Journal of Medicine, looked two types of PM – PM2.5 and PM10.

Also, a recent study has concluded that exposure to air pollution, particularly during the first 10 years of life, could play a significant role in the development of psychiatric disorders. However, not everyone is convinced by the data.

The study, which appears in PLOS Biology, used data from the United States and Denmark to uncover the possible link between environmental pollution and psychiatric disorders.

The new research found that rates of both bipolar disorder and depression were higher among those living in areas of poor air quality.

The researchers also concluded that Danish people who lived in polluted areas during their first decade of life were more than twice as likely to have personality disorders and schizophrenia.

With mental health in the spotlight, researchers are keen to understand the factors that influence whether or not someone develops psychiatric illness.

There are a multitude of potential causes, including genetics as well as life experiences, so it is not possible to exclude environmental factors.

In this new study, the team looked more closely at how a specific environmental factor — air pollution — affects the brain and the likelihood of psychiatric disorders.

To reach their conclusion, the researchers drew from two large datasets. The pollution information for the United States (U.S.) came from the Environmental Protection Agency’s (EPA) air quality measurements, while for Denmark, the researchers looked at the national pollution register.

The EPA track 87 different air quality measurements. Although the Danish pollution register monitors fewer measurements, they have a higher spatial resolution.

The team then looked at healthcare data. For the U.S., they accessed a health insurance database that included claims that more than 151 million individuals made between 2003 and 2013.

For Denmark, they used data for all of the residents who were born in the country between 1979 and 2002 and were living in Denmark on their 10th birthday.

Denmark assigns each person a unique identifying number that links information from national registries. This information enabled the researchers to estimate air pollution exposure during the first decade of life. However, the researchers were not able to be quite so specific with the U.S. dataset, as they were limited to the county level.

According to the authors, the findings showed that air pollution did have links to various psychiatric disorders. Using Denmark’s more specific records, the researchers were able to pinpoint that the developing brain during a person’s first 10 years of life might be a bit more prone to the effects of air pollution.

Also, air pollution’s deadly effects on health are well known, but scientists now fear it could turn some people into violent offenders.

When the air is dirtier, more violent crime is committed, researchers found after conducting a huge study into 13 years of data on 86 million people in the United States.

Airborne particles and noxious gases could interfere with the proper functioning of the brain, making people more likely to act aggressively, the researchers believe.

The study, just published in the online version of the journal Epidemiology, is likely to lead to further calls for British cities to clean up their act, by showing that air pollution can affect behaviour, not just physical health.

Meanwhile, a major study suggests air pollution nearly doubles the risk of suffering a debilitating form of visual impairment.

People living in areas with high levels of traffic emissions are twice as likely to suffer from age-related macular degeneration (AMD), researchers found.

Scientists found long-term exposure to nitrogen dioxide – a pollutant that is especially linked to old diesel cars – increased the risk of AMD among over-50s by 91 per cent.

And those living in high areas of carbon monoxide, which is linked to petrol and diesel, saw risk go up 84 per cent. AMD is one of the most common causes of visual impairment.

Last year scientists revealed they had found tiny particles of vehicle soot in the womb of pregnant women, suggesting even unborn babies are at risk.

The new research – the first to examine the link between air pollution and AMD – suggests fumes are affecting people from the cradle to the grave.

The researchers, whose work is published in the BMJ Journal of Investigative Medicine, assessed the health records of 40,000 people between 1998 and 2010.

The team compared air pollution levels in the areas they lived to their chance of developing AMD.

During the monitoring period, 1,442 people developed the condition.

The researchers, from China Medical University in Taiwan, found the 25 per cent of people living in areas with the highest levels of air pollution were nearly twice as likely to develop AMD than those in the 25 per cent with the lowest levels.

The academics stressed their study did not look at the biological link between pollution and eye problems – merely the statistical odds linking the two.

But they pointed out that previous research has found airborne pollution interferes with the central nervous system, which may also explain the mechanism by which car emissions hit the retina.

“Recent studies have linked nitrogen dioxide pollution to the cardiovascular and neurological systems,” they wrote.

“High nitrogen dioxide is associated with various brain diseases including low cognitive function and a lower functional integration in children, Parkinson disease, stroke, and dementia.

“Notably, the retina is also a part of the central nervous system which is biologically reasonable to be vulnerable to nitrogen dioxide intoxication.”

Dr. Andrey Rzhetsky of the University of Chicago, IL, who led the study said: “We hypothesized that pollutants might affect our brains through neuro-inflammatory pathways that have also been shown to cause depression-like signs in animal studies.”

Computational biologist Atif Khan, who is the first author of this study, comments on the findings. He says, “The physical environment — in particular air quality — warrants more research to better understand how our environment is contributing to neurological and psychiatric disorders.”

Although the results are interesting, the study does have significant limitations and has caused much debate, as Rzhetsky himself explains.

He says, “This study on psychiatric disorders is counterintuitive and generated considerable resistance from reviewers.”

In fact, there was so much division that the journal decided to publish a companion article alongside the research paper. Prof. John Ioannidis, a scientist who assisted in the journal’s editorial process but who is not connected with the original study, is the author.

In the article, he picks apart the data. Among other criticisms, he explains how “results from the U.S. data offer mostly coarse, exploratory hints. Associations may be entirely spurious or, conversely, important associations may be missed because of these deficiencies.”

Prof. Ioannidis eventually concludes that a “causal association of air pollution with mental (conditions) is an intriguing possibility.”

“Despite analyses involving large datasets,” he adds, “the available evidence has substantial shortcomings and a long series of potential biases may invalidate the observed associations. More analyses by multiple investigators, including contrarians, are necessary.”

In conclusion, the theory that pollution impact mental health will require a great deal more evidence before mainstream scientists begin to take it seriously.

Meanwhile, two million people in London alone are still living in areas with illegal levels of air pollution, according to a recent report from the London Atmospheric Emissions Inventory.

That crowded and polluted cities experience more violent crime is not surprising.

But researchers did not simply look at whether more violent crime was committed in polluted places. Instead, they looked at how recorded offences rose and fell over time in 301 diverse counties across the US – urban, suburban and rural – and whether there was any link to air pollution readings.

Put simply, they asked if crime went up when air pollution rose. For non-violent crimes such as theft, the answer was ‘no’. But for violent crime a correlation did emerge.

The research team, from the University of Minnesota School of Public Health and Colorado State University, wrote: “Our study identifies an association between air pollution and county-level violent crime… We find that violent crime increases by 1.17 per cent for each 10-microgram-per-cubic-metre increase in daily [fine] particulate matter, and 0.59 per cent for each 10-parts-per-billion increase in daily ozone, with most of the effect driven by increases in assaults.”

Violent crime went up when the air was more polluted both in poor and rich areas. Previous studies in mice and dogs have found those animals exposed to high levels of fine particulate matter – found in diesel fumes – exhibit “increased aggressiveness, territoriality, and bias towards immediate rewards,” they noted.

“Likewise, air pollution exposure may increase anxiety, which can lead to criminal and unethical behaviour,” they went on.

“An impulsive and aggressive response may explain why air pollution is associated with increased violent, but not non-violent crime.

“We cautiously interpret this result as evidence for acute neurological and behavioural health effects of air pollution and need to further investigate the effect pathway.”

They also pointed out that previous research has “indicated that metallic constituents of particulate matter, notably manganese and mercury, may contribute to more aggressive and violent behaviour.”