Have you ever heard of pollution killing someone? I saw this question posted in response to a blog denouncing "eco-condriacs". With June 2 being Clean Air Day, it's an appropriate question to consider.
It's often difficult to pinpoint direct proof of pollution's harmful effects on human health, except in cases of acute poisoning. The most famous and tragic example of acute pollution poisoning is the Great Smog of London in December 1952, which killed 3,000 people in one week. A total of 12,000 deaths were attributed to the smog over the course of the following year.
This event and many others prompted researchers to examine the health effects of air pollution at lower levels but over an extended period of time.
Burning fossil fuels (gasoline, kerosene, diesel, oil, coal) loads the air with pollutants, including "fine particulate matter", that we now know can affect cardiovascular health. Around the world, research teams have conducted experiments on isolated arterial cells, laboratory rats, healthy volunteers and cardiac patients. The data show that breathing tailpipe exhaust increases blood coagulation and causes oxidative stress of the arteries. It can lead to constriction of the arteries, reduced blood circulation in the vessels of the heart muscle, higher blood pressure, arrhythmias and thromboses. Several studies demonstrate that these air pollution-related effects can induce atherosclerosis (hardening and blockage of arteries that can result in insufficient blood supply to the tissues and organs).
A German researcher documented in 2007 that people living within 50 metres of a highway have 63 per cent more coronary calcification than those living more than 200 metres away. This solved a mystery I had been pondering over the years as I performed cardiac catheterizations. Why do some patients have so much calcification in their arteries while others don't, in spite of seemingly similar risk factors? The answer is that our bodies respond to environmental conditions.
- In Italy, rising levels of fine particulate matter in the air were linked to a dramatic increase in cases of thrombophlebitis (a condition whereby the veins become inflamed and occluded as a result of blood clotting).
- Studies in China, Taiwan, Portugal, Finland and nine large American cities documented that more stroke fatalities occur when the concentration of fine particulate matter increases.
- Following air-pollution episodes in Boston in 1995 and 1996, the number of heart attacks increased by 48 per cent in the first two hours and by 69 per cent in the 24-hour period after pollution levels peaked.
- Considering broadly the impact of air pollution on heart health and blood vessels, a large-scale American study found that when the concentration of fine particulate matter increases by 10 micrograms per cubic metre of air, cardiovascular-related mortality increases by 12 per cent among non-smokers and by 94 per cent among smokers. Arrhythmia and heart failure or infarction (tissue death caused by obstruction of the blood supply) also increase by 13 per cent and 72 per cent respectively.
No wonder our emergency rooms become so crowded during smog episodes! Ever since this research was published, I check the smog forecast whenever I'm on duty in the emergency room. I can often tell how busy my day will be based on the air-quality rating.
Conversely, the beneficial effects of antipollution standards can also be measured: reducing the concentration of particulate pollution by 10 micrograms per cubic metre improves life expectancy by 0.6 years. Therefore, measures that improve air quality would likely have a similar effect to restrictions on smoking in public spaces. The latter led to drops in hospitalization for acute infarctions by 11 per cent in Rome, 13 per cent in Saskatoon, 17 per cent in Scotland and 27 per cent in Colorado.
An interesting British study offers a broader perspective on the connection between the environment and heart health. Researchers analyzed cardiovascular mortality trends based on patients' exposure to green space. They classified neighbourhoods according to five categories of "greenness," from the least green (the concrete downtown area) to the greenest. It is well established that lower socio-economic status goes hand in hand with higher rates of illness, including cardiovascular disease. However, the ratio of cardiovascular-related deaths among the poorest quarter of the population compared to the richest quarter dropped spectacularly from 2.19 in the least green area to 1.54 in the greenest area. No treatment to date has been this effective in reducing the social inequalities of illness.
In the past 20 years, interventional and preventive cardiology have enhanced clinical cardiology. Now environmental cardiology's time has come.
It is not up to cardiologists to determine the best way to reduce air pollution. But it's clear that alternative sources of energy must be quickly developed and that green is not just a new "brand". It's our health.
Dr. François Reeves is an interventional cardiologist and associate professor of medicine at the Université de Montréal.