Dust to dust: effects of airborne particulates (and ground level ozone) on human health

Mexico City

Particulates (airborne particles of solid matter, and tiny droplets of liquid matter with dissolved components) include a wide variety of substances, from inorganic mineral and rock particles to organic dust

Are All Particulates Harmful? No !

Not all particulates have adverse effects on human health.

For example, volcanic eruptions emit huge amounts of inorganic particulates (ash) into the atmosphere that, in natural concentrations, do not harm humans to a significant degree

Also, there is also no evidence that sea salt -- another form of inorganic particulate in the atmosphere, results in adverse effects on health.

But…is good evidence to link some particulates from combustion to serious effects on health

The key is CONCENTRATION. High enough concentrations of any particulate can be bad. Also, some particulates are more harmful than others in terms of how they interact with the functioning of the human body.

On a large scale, much of our “pollution” comprises abundant dust generated from open sources (e.g. open fields, roads, etc.), transportation, combustion of materials and industry/mining

Principal types and sources of air pollution in Canada per unit mass

Particulate pollution is not restricted to urban areas

From a public health perspective, air-borne small particulate from combustion (e.g. wood burning) and open pit mining, is now considered to be the single greatest air pollution problem in British Columbia.

Scientific research indicates that increased levels of this small particulate are responsible for a marked increase in Emergency Room visits, hospitalizations, and days lost from school and work.

Study by American Lung Association (1995):Indicated that air pollution from particulates, produced by the burning of fossil fuels and other materials, was determined to have caused thousands of deaths and cost the national economy some $11 billion (US) each year

Particulate air pollution has been closely linked to aggravation of existing heart and lung conditions and even increased death rates (puts stress on respiratory system).

Children and senior citizens are most vulnerable -- a recent study estimated that small particle pollution is responsible for many thousands of premature deaths annually in the North America.

Studies of small particulate air pollution also indicate a significant increase in the population death rate in areas suffering prolonged exposure to this type of pollution.

General Consequences on Human Health

Perhaps one can get a better appreciation ofparticulate pollution by looking at an urban setting

Welcome back to Beijing -but are we really in the position to point the finger ?

Smog: A Common Urban Problem

What is smog ?: Word derived from “smoke” and “fog”

What is smog made of ?: A variety of substances, but primary components are particulates (solids and liquid droplets) and ground level ozone (O3)

What kinds of particulates ?- Solid particles emitted from combusted material- Volatile organic compounds (VOCs): compounds of mostly carbon and hydrogen, but which also contain oxygen, nitrogen, chlorine, sulphur and phosphorus (sources: motor vehicles, evaporated of gasoline, oil-based paints, nail polish remover, barbecues, surface coatings, inks and hydrocarbons from the petrochemical industry)

One would think it is from solid particles. But while solid particles do occur in smog, it is mostly the nitrogen dioxide that colours the stagnant air.

What makes smog hazy and brown ?:

Toronto

Montreal

HamiltonLondon (the other one)

What conditions cause smog ?

High particulate content of air

Plus certain weather conditions, especially:-warm temperatures ranging from the high 20s up

-still, stagnant air (slow wind speeds)

Often associated with thermal inversion, when warm air mass presses down on lower, cooler air mass, trapping pollution-laden air close to the ground

Tends to occur in densely populated urban areas (duh!) and valleys where warm air masses become trapped and remain stagnant Smog season in Canada: about May through September

Worst places in Canada for smog:•the urban belt running from Windsor to Quebec (some from Canada, lots from U.S. in summer)•Atlantic Canada (mostly from polluted air of urban centres along the eastern United States- thank you G. dubyuh ! )•Lower Fraser Valley (British Columbia)

Worst time of the day for smog: late afternoon to early evening

Where and when does smog occur ?

Note wind direction !Call it free trade

But isn’t lots of ozone a good thing ?

Ground-level ozone is the same kind of ozone found in the stratosphere (15 to 30 kilometres above the ground) that shields us from the sun's harmful ultraviolet rays.

Ozone (O3) is basically just regular oxygen molecule (O2) combined with another oxygen atom. But ozone is formed differently in the stratosphere than at ground level

Stratospheric ozone is produced when oxygen molecules are split into atoms when bombarded by uv radiation. The single atoms (O) then combine with regular oxygen molecules (O2) to form ozone (O3) .

Ground Level OzoneGround level ozone forms in a different way (is dependent on high concentrations of pollutants)

Involves nitrogen oxides and a variety of organic molecules that split apart in strong sunlight

For example, a single oxygen atom is given off by this reaction:

NO2 + uv light = NO + O

The lone oxygen atom then combines with a regular molecule of oxygen (O2) to form ozone (O3):

O + O2 = O3

More complex reactions also occur (especially those involving organic compounds), but you get the point

So the formation of ground level ozone feeds onother pollutants generated by fossil fuel use on warm, sunny, summer days

Ground Level Ozone

At ground level, high levels of ozone can harm people, animals and vegetation (it is very reactive- hence its use in killing bacteria in the purification of bottled water)

-irritates lung airways

-short term symptoms include wheezing, coughing, pain when taking a deep breath, and breathing difficulties

-may cause permanent lung damage after long-term exposure

-in plants, high levels of ozone prevent plants from producing and storing food (in turn makes them more prone to disease, pest infestations, and harsh weather).

Effects of High Levels of Ground Level Ozone

How does smog affect humans ?

So…on a general level, we can say that smog affects the cardio-respiratory system of people. More specifically, it can cause:

•mild respiratory distress•coughing•asthma•bronchitis•reduced resistance to lung infections and colds •eye irritation

Obviously, symptoms tend to be worst when smog is worst

Also, volatile organic compounds, many of which are not terribly dangerous themselves, can serve as vehicles for carcinogenic organic molecules that normally occur in trace quantities (so possible long-term implications to smog exposure)

What do I do when there is a smog warning ?

reduce physical activity, especially activity outside.

restrict the amount of time young children spend outside.

people with pre-existing respiratory problems should consult their physician about how much time to spend outside and what precautions to take.

End of lecture