Where Does Particulate Pollution Come From and What Can I Do About It?

PM2.5 have been killing us forever, but we never knew how bad they were.

Two men smoking on street corner

University of Pittsburgh

Last week, while teaching my class, there was a sudden strong smell and my eyes started watering. Evidently, a student on the second floor set their plastic coffee mug on fire in the microwave oven. There was not enough smoke to set off the fire alarms, but enough to set off my own internal alarms, and I sent everyone home. This week, I decided to talk about air pollution, and in particular, the danger from the really tiny particulates known as PM2.5. We used to be breathing them all the time, thanks to emissions from industry (like above in Pittsburgh in 1940 and thanks to cigarettes).

Indoor barbecue
Indoor barbecues are good for air quality!.

James Vaughan/Flickr

I am not sure how many people actually barbecued over charcoal in their homes when they had a party, but almost everyone smoked, and the idea of second-hand smoke being harmful hadn't even been invented. PM2.5 effects on health really couldn't be separated from all kinds of other environmental hazards, and even today a list of effects will vary from source to source. The Province of Ontario's list:

Exposure to fine particulate matter has been associated with hospital admissions and several serious health effects, including premature death. People with asthma, cardiovascular or lung disease, as well as children and elderly people, are considered to be the most sensitive to the effects of fine particulate matter.

New York State:

Particles in the PM2.5 size range are able to travel deeply into the respiratory tract, reaching the lungs. Exposure to fine particles can cause short-term health effects such as eye, nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath. Exposure to fine particles can also affect lung function and worsen medical conditions such as asthma and heart disease. Scientific studies have linked increases in daily PM2.5 exposure with increased respiratory and cardiovascular hospital admissions, emergency department visits and deaths. Studies also suggest that long term exposure to fine particulate matter may be associated with increased rates of chronic bronchitis, reduced lung function and increased mortality from lung cancer and heart disease. People with breathing and heart problems, children and the elderly may be particularly sensitive to PM2.5.

DEFRA in the UK:

The biggest impact of particulate air pollution on public health is understood to be from long-term exposure to PM2.5, which increases the age-specific mortality risk, particularly from cardiovascular causes. Several plausible mechanisms for this effect on mortality have been proposed, although it is not yet clear which is the most important. Exposure to high concentrations of PM (e.g. during short-term pollution episodes) can also exacerbate lung and heart conditions, significantly affecting quality of life, and increase deaths and hospital admissions.

credit: Classic Film on Flickr

We learned that smoking was bad for our health, but perhaps missed in all that smoke was the danger from the campfire burning away. Because the PM2.5 stuff is clearly more damaging than we ever knew. The American Heart Association writes:

Exposure to PM <2.5 μm in diameter (PM2.5) over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years.

Another study notes that "long-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality."

credit: Google Street View/ condos on gardiner

It gets worse. Emily Underwood writes in Science that "a growing body of evidence suggests that exposure can also harm the brain, accelerating cognitive aging, and may even increase risk of Alzheimer’s disease and other forms of dementia."

The link between air pollution and dementia remains controversial—even its proponents warn that more research is needed to confirm a causal connection and work out just how the particles might enter the brain and make mischief there. But a growing number of epidemiological studies from around the world, new findings from animal models and human brain imaging studies, and increasingly sophisticated techniques for modeling PM2.5 exposures have raised alarms.

A Canadian study also found that people living within 50 meters (164 feet) of busy highways had a seven percent higher likelihood of developing dementia.

where I wondered why cities let people build so close to highways.

We know from previous research that air pollutants can get into the blood stream and lead to inflammation, which is linked with cardiovascular disease and possibly other conditions such as diabetes. This study suggests air pollutants that can get into the brain via the blood stream can lead to neurological problems.

Residential heating

credit: Dominique Imbert

It varies, all over the world. In Ontario, Canada where I live and where no coal is burned for generating electricity, the single biggest source is residential heating at 39 percent, with transportation in second place at 19 percent. In Alaska. 73 percent comes from burning wood. We have discussed this a number of times on TreeHugger, but as the dangers of PM2.5 become more clear, it is becoming also clear that as charming and beautiful as fireplaces and wood stoves are, we should not be burning wood at all.

Diesel exhaust

credit: Simone Ramella

In many parts of the world, the exhaust from cars is a major source of particulate pollution. Sami has written of a new study linking diesel emissions to 1 in 4 air pollution deaths.

With government figures for 2008 showing 29,000 people dying prematurely from air pollution each year, diesel fuel burned in vehicles could be responsible for around one in four of all air pollution deaths, said Frank Kelly, professor of environmental health at King's College, London. "We have walked blindly into a situation where we have a high percentage of diesels in the transport sector. All taxis and buses are diesel. From one in 10 private cars being diesel in 2000 it is now nearly half today. A lot of the minute particulate matter [emitted from exhausts] comes from diesels in cities. It is estimated that 50% of the particulate matter in London is from transport and that diesel makes up about half of all the transport," he said.

Car tires and brakes

credit: Wikipedia/ charging cars in Ontario

Boy, did I get in a lot of trouble for writing Do electric cars generate as much particulate pollution as gas and diesel powered cars? The answer is of course, they do not. But they do produce some; tire, brake and road wear are thought to produce as much as half the particulates that come from transportation. That's one of the reasons I do go on about how electric cars are still cars, and heavier cars are worse than light cars, whether gas or electric.

Forest fires

credit: NOAH BERGER/AFP/Getty Images | Part of the Mendocino Complex Fire, August 5, 2018.

We seem to be having more and more forest fires thanks to crazed environmentalists climate change, and they are significantly increasing PM2.5 levels. Last summer's California fires created "the worst air quality ever experienced in San Francisco", an "air quality emergency."

Particulate matter is the "number one environmental killer in the world," [Dr Daniel] Jacob said, and "the levels that are present in those areas affected by wildfires are like you might expect on a very polluted day in China or India."

Coal-burning power plants

credit: Lloyd Alter/ From the forbidden city

In China and India, the biggest problem is industrial and energy production from burning coal. In the US the particulate pollution has dropped, primarily because there has been such a big switch to natural gas, which produces far lower levels of PM2.5. But cars are catching up; according to China Daily,

Coal burning is no longer a major source of PM2.5 in Beijing, while car emissions have become the top cause, according to a study released by Beijing's environment watchdog. Emissions from vehicles, ships, and construction machinery are the top sources of PM2.5 (particulate matter of diameter less than 2.5 micrometres), contributing up to 45 percent of the total pollutants in Beijing, according to the study by Beijing Environmental Protection Bureau.

Local sources: wood-fired commercial cooking

credit: St-Viateur bagel shop in Montreal/ Lloyd Alter

Not all PM2.5 particles blow in from afar; some sources are surprisingly local. Wood-fired pizza, Portuguese chicken and bagel shops put out a lot of it, because wood seems to be made of solid PM2.5. In Montreal, they are even considering banning wood-fired bagels, which makes sense since they are smack in the middle of a residential area and are surrounded by schools and daycare centers. One neighbor complained, not between chomps of a St. Viateur bagel:

This industrial activity in a residential neighbourhood is harmful, toxic and outdated,” said François Grenier, who lives in Mile-End near Fairmount Bagel. “That chimney has to come down or be relocated. The procrastination has to stop. The city and Fairmount Bagel both know it: our quality of life has been compromised for decades ... they have to stop poisoning us.

Really local sources: your kitchen stove

credit: Gabriel Rojas/ Photo Lloyd Alter

Finally, I will flog this horse one more time: the kitchen stove is a major source of PM2.5. In much of the world, cooking is the single worst source, cooking over wood without proper ventilation; in developed countries, it is really just slightly better, where we cook with gas and pretend noise-making exhaust hoods. One expert noted:

Frying, grilling or toasting foods with gas and electric appliances creates particulate matter, nitrogen dioxide, carbon monoxide and carbon dioxide, and volatile organic compounds....Emissions of nitrogen dioxide in homes with gas stoves exceed the Environmental Protection Agency’s definition of clean air in an estimated 55 percent to 70 percent of those homes, according to one model; a quarter of them have air quality worse than the worst recorded smog (nitrogen dioxide) event in London.

Recirculating hoods have been described as being as useful as recirculating toilets, but even hoods exhausting to the outside are often badly designed. I have always said that this is why we should have separate, not open kitchens; one commenter suggested that we should design our kitchens like paint booths, with their own totally separate ventilation system.

What's wrong with this picture?

credit: PETER PARKS/AFP/Getty Images

When the Woobi face mask was released I complained "what kind of a world do we live in now that we have to send our children out in masks, where 300 million kids can't breathe fresh air?" Is this the future we want? It is the future we have, but we just didn't realize it. PM2.5 has been around forever, and who knows what proportion of deaths, how many years have been lost because of them. But it seems every week there is another study showing what a killer they are. It is time to take them very, very seriously.