Death in the city. (Urban).

Hacking and wheezing through smog alerts is becoming a frequent experience for Canada's city dwellers. And, as 78% of Canadians live in urban areas, that means most of us.

By far the largest and worst affected area is southern Ontario. This heavily populated region creates enough air pollution on its own to cause plenty of coughing and spluttering. But, the quantity of locally generated pollutants is doubled by contributions from the United States. A southerly flow of air pumps thousands of tonnes of soot and gases, from coal-fired power stations and industry in the Ohio Valley, up into Ontario.

Now, add a blistering July sun; all the goop in the air cooks in the heat to form what the experts call photochemical smog. (Smog is a word created from combining parts of the words "smoke" and "fog".)

The recipe for photochemical smog includes a list of noxious substances with long chemical names. The result is a brownish haze that does bad things to most life forms.

The most obvious results of exposure to smog is that peoples' eyes start watering, the air we breathe tastes of sulphur, and the inside of shirt collars turn black. Most people find these effects irritating but, more sinister stuff is going on.

For people with breathing problems such as asthma or emphysema, a smoggy day can mean a trip to hospital. Frequent or prolonged exposure can mean a trip to the morgue.

Many of the chemicals found routinely in the air we breathe are what's called carcinogenic, or cancer causing. Benzene is a known villain and people who work at gas stations may be getting more than their fair share of it. About one percent of gasoline is benzene and it's vented off as a vapour from the fuel. There is a similar problem with dry-cleaning stores. Tetrachloroethylene is used as a cleaning agent, and it's thought to cause cancer.

There are ten particularly worrisome chemicals (polycyclic aromatic hydrocarbons, chromium 6, and formaldehyde are among them). Toronto's public health department found nine of them in the city's outdoor air in concentrations close to or above safe levels.

In their 2002 report, health officials wrote: "This study indicates that Toronto residents are routinely exposed to a variety of carcinogenic chemicals in the environment, and that these exposures are associated with a lifetime cancer risk greater than one in a million excess cancers."

The city's medical officer of health, Dr. Sheela Basrur points out the difficulty this air pollution causes for people. "You can avoid smoking," she told a news conference, "but you cannot avoid breathing. If you go into a polluted environment or if you live in a neighbourhood that has a high-traffic density there is not much you can do, short of moving, but to where? There is no unpolluted, safe environment these days."

KILLER SMOG

December 1952 was a very bad time to be living in London, England. The city's power stations were fuelled by coal, and almost every home was heated by a coal fire. Thousands of trains a day entered and left the capital pulled by coal-fired steam engines. And, factories using coal added to the sulphurous cloud of smoke that was trapped over the city by a weather pattern. At ground level, the smog was so thick that visibility was less than one metre. In the space of five days more than 4,000 people died as a direct result of the smog. Four years later, the Clean Air Act was introduced banning the use of smoky fuels such as coal.

SMOGGY FACTS

According to the Clean Air Alliance, emissions from the coal-fired generating station at Nanticoke, Ontario cause 1,000 premature deaths a year in Toronto.

According to another estimate, 40 Canadians die from air pollution-related causes every day.

Two-stroke engines, commonly found on lawn mowers, leaf blowers, weed-whackers, etc., can emit up to 20 times more pollution than four-stroke engines.

The safe level of a cancer-causing chemical is defined as a concentration that causes one extra person to die prematurely of cancer among every one million residents over their lifetimes.

TREES TO THE RESCUE

Chicago is a city of about three million and, as with many cities, it has more trees than people. This "urban forest" performs a lot of useful tasks. Trees absorb pollution and a landmark study in 1994 put some numbers on this activity. The study found that Chicago's urban forest removes nearly 750 million kilos of pollutants from the air each year. To do the same work, pollution-control equipment costing $9 million U.S. would have to be installed. In addition, trees provide summer shade and cut winter cold so that heating and air conditioning costs are lower. They reduce water run-off and erosion, filter dust, block noise, and create a habitat for songbirds. They also absorb carbon dioxide and give off oxygen.

FACT FILE

Sweden has imposed a tax on carbon dioxide emissions and the proceeds are invested in renewable energy development and public transit. Canada has no such program.

Websites

Cleanair Canada--http://
www.cleanair.ca/

Toronto Environmental Alliance--http://www.
torontoenvironment.org/