Particulate Matter: Impacts
Health
What is Particulate Matter?
Particulates, also known as particulate matter or PM, are very small particles that come from
a variety of natural and human-produced sources — and a range of sizes. Two of the most common sizes of classifications are PM10 and PM2.5.
PM10 represents particulate matter less than 10 microns in diameter, while PM2.5 (a subset of PM10) represents those particles of diameter less than 2.5 microns. Often PM2.5 is referred to as the fine fraction of PM10. The fraction of PM10 containing particles with diameters greater than 2.5 microns is termed the coarse fraction. (Microns are also referred to as "micrometres."*
The smaller particulates — PM2.5— most frequently are the result of combustion activities and chemical reactions in the atmosphere. When emitted directly from their source, these particles are considered "primary." The particles that are formed as a result of chemical reactions in the atmosphere are considered "secondary."
The larger, more coarse particulates generally come from natural sources, such as
wind-blown dust, sea salt spray and vegetation. They are also emitted from
human-produced sources, including road dust, and various grinding activities.
Because of their relatively large size, these particles tend to settle out of
the atmosphere much more quickly than fine particulates, in a few hours to a few
days. Fine particulates, on the other hand, can stay in the air for days to
weeks.
In our bodies, too, coarse particulates are not a major problem: they tend to be removed in the
upper portions of our respiratory system — our nose and throat — before they can get into our lungs. Fine particulates, however, can penetrate deep into our lungs, collecting in the tiny air sacs (called "alveoli") where oxygen enters the bloodstream. As a result, they can cause breathing difficulties and sometimes permanent lung damage.
Fine particulates are much more complex chemically than coarse particulates, a factor which may affect their inherent toxicity. They are often composed of harmful substances — for example, toxic trace metals like lead and cadmium, polycyclic aromatic hydrocarbons (PAHs: it is suspected that some PAHs cause cancer), volatile organic compounds (VOCs), carbon monoxide and formaldehyde.
The Health Impacts of Fine Particulates
Fine particulates are now considered to be the worst local air pollution problem in BC, from a public health perspective.They are a more serious threat to our health than ground-level ozone — the main, toxic ingredient of smog. That's the conclusion of two reports in 1995 and 1993, by Dr. Sverre Vedal of the University of British Columbia, for the Ministry of Environment and the Provincial Health Officer respectively.
Fine particulate air pollution triggers many kinds of respiratory illnesses,
including asthma, bronchitis, pneumonia and emphysema. Senior citizens, infants
and people who already have lung, asthmatic or heart problems are most at risk,
but healthy younger adults and children can also be affected.
Exposure to high levels of fine particulates is associated with a significant rise in the
number of premature deaths from respiratory and heart disease. Over 1.2 million
Canadians suffer from asthma, and it is the most common cause of medical
emergencies in children. Fine particulate pollution and asthma are an unhealthy
and unwanted mix.
Dr. David Bates, a medical doctor with expertise both as a respirologist and in the human health
effects of air pollution, provided testimony during an Environmental Appeal
Board Hearing (February - March 2000) related to beehive burner emissions of
particulate matter in Houston and Smithers.
In an unpublished letter related to the hearing, Dr. Bates referenced numerous epidemiological studies that show a consistent relation between daily changes in PM10 and PM2.5 concentrations and health effects including:
- daily respiratory and cardiovascular mortality;
- hospital admissions for acute respiratory disease;
- hospital admissions for cardiovascular disease;
- emergency visits for acute asthma in adults and children;
- fluctuations in the pulmonary function of asthmatic children;
- cough incidence in asthmatic children; and
- family practice consultations for asthma and respiratory disease.
At this point, there is no known threshold for health effects related to particulate matter,
which suggests that even if small quantities of this pollutant are emitted, they
can trigger health problems. Dr. Bates pointed out that 24-hour averages (such
as those used in air quality index calculations) are probably not appropriate to
represent conditions that might have a significant impact on a population. This
could relate to localized conditions or short-term exposures.
From his examination of hourly and 24-hour PM10 data for Smithers and Houston, Dr. Bates concluded that “these levels are likely to be causing some or all of the adverse health impacts” listed above. Data for other communities in the Skeena Region were not examined, given the nature of this communication. See below (unpublished letter) for reference.
For more information on particulate matter, including related health effects, visit the Particulates website of the Environmental Quality Branch. See also "Particulate Matter" Air Pollution BCHealthFiles, Health File #65e.
Vedal, S., 1995. Health Effects of Inhalable Particles: Implications for British Columbians.
Vedal, S. 1993. Health Effects of Wood Smoke: A Report to the Provincial Health Officer of British Columbia.
Contact the Provincial Health Officer at (250) 952-0876
Bates, D., 2000. Unpublished letter to T. Howard (Sierra Legal Defence Fund) Re: Mutschke et al. v. Jan 26, 1999 Decision of Assistant Regional Waste Manager re: Waste Permits PA-01691 / 05339 / 01543.
Environment
Particulate matter in the atmosphere can also reduce visibility, through its ability to scatter and absorb light. Fine particles in the size range of about 0.1-1 microns in diameter can cause the greatest reduction in visibility. The reason is that these particles' diameter is about the same size as the wavelength of visible light, which makes them able to block out light.
In the Skeena Region, mountains can become hazy or even obstructed from view altogether. These environmental effects are serious from a road- and air-safety perspective, in addition to the economic impacts they can have on local tourism.
Visibility degradation from smoke can interfere with vehicle and air transportation. Large volumes of smoke can obscure the landscape for pilots using visual navigation. This is not an unknown hazard to charter operators flying tourists into the backcountry, from locations along the Highway 16 corridor.
Another significant problem, for residents and tourists alike, is that the scenery can be hard to see or even blotted out behind a swath of smoke. Professional photographers visiting or living in the region may have second thoughts about working with such a landscape.
The soiling effect of particulate matter is another environmental impact and has been experienced in communities such as Port Edward, in the western portion of Skeena Region. When particulate matter falls out of the atmosphere it can accumulate on people's cars, laundry drying outside, and in their homes.
Microns, Micrometres and...Micrograms!
When we talk about the diameter of PM, we use microns (micrometres) — "µm" (so PM2.5and PM10).
When we refer to the concentration of PM, we use micrograms — "µg" ("µg/m3" is the concentration term we use).
updated: may 2006
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