Even “safe” levels of air pollution can cause heart attacks, a study suggests.
Researchers also found that people can be knocked down within an hour of inhaling dirty air.
Stricter air quality standards are now urgently needed, experts claimed.
Levels of nitrogen dioxide (NO2) – mainly emitted by cars – were tracked for 15 years in nine US cities.
Scientists at Columbia University then compared this to hospitalizations for heart attacks, helping them pick apart every possible link.
Even “safe” levels of air pollution can cause heart attacks, a study suggests. Researchers also found that people can be knocked down within an hour of inhaling dirty air
Air pollution increases the risk of several conditions, including heart attack, stroke and diabetes
What is Nitrogen Dioxide?
Nitrogen dioxide (NO2) is a gas that is mainly produced by the combustion of fossil fuels.
Short-term exposure to NO2 concentrations can cause inflammation of the airways and increase susceptibility to respiratory infections and allergens.
NO2 can worsen the symptoms of people who already suffer from lung or heart disease.
As the concentration of the pollutant increased, so did the risk of heart attacks, just 60 minutes after NO2 levels peaked.
The increased risk of heart attack started when NO2 levels fell below current US national standards of 100 parts per billion (ppb).
This threshold means that for every billion units of air, 100 units of NO2 are considered acceptable.
These are in line with World Health Organization and UK air standards that the hourly concentration should not exceed 200 micrograms of NO2 per cubic meter of air (µg/m³). 100 ppb NO2 corresponds to 191 µg/m³.
UK laws currently state that hourly levels of toxic NO2 must not exceed that threshold more than 18 times a year.
However, air quality monitoring tools show that this limit is regularly exceeded in parts of London.
Write in the journal Environment Internationalsaid the academics: ‘Our findings suggest that current hourly norms may be insufficient to protect cardiovascular health.’
Studies have repeatedly shown that air pollution, especially from traffic, can cause a heart attack.
This is because breathing in pollutants — which can be so small that they travel deep into the lungs and bloodstream — can restrict blood flow to the heart and force the organ to work harder than usual.
Pictured is a graph showing three measurements of nitrogen dioxide, a pollutant produced primarily by engines and the burning of fossil fuels. The annual average of the urban background (purple) decreased by almost a quarter (23%) in 2020
However, it is unclear when the risk of heart problems starts after exposure to pollution and how long it lasts.
The Columbia University team used data on hourly NO2 concentrations for cities in New York State between 2000 and 2015.
The study also included hospitalization data from 8.9 million people, including 350,000 who had a heart attack.
Average NO2 concentrations per hour were approximately 23.3 ppb.
But every 10 ppb increase apparently increased the risk of heart attacks by 0.2 percent.
And the risk of heart attack was highest in the first hour of exposure, when it increased by 0.21 percent.
The risk increased for six hours after peaks in NO2 levels in all cities and remained high for up to 24 hours in some cities.
Every year about 100,000 Britons and 800,000 Americans have a heart attack.
The WHO has demanded that countries take tougher measures as evidence mounts on the health risks of minor pollutants, which have also been linked to dementia and cancer.
According to the UN agency, poor air quality causes an estimated 7 million deaths each year and reduces the lives of millions of healthy years.