Is SMOG the real culprit in lung cancer?
We’ve blamed smoking, but there is chilling evidence that soot and gas fumes in the air are powerful factors too. It poses a life-and-death question: When will we clean up our cities?
The federal minister of justice, Stuart Garson, told the House of Commons in February that the air is being dangerously polluted by the exhaust fumes from cars and trucks, and that as soon as a fume-control device can be perfected it should be illegal to drive a vehicle without one.
Flis statement underlined a change in the thinking about smoke in relation to our general health, and particularly to lung cancer. In recent years a heated medical controversy has spun around the question, "Do cigarettes cause lung cancer?" Now a new question is being asked, “Is lung cancer caused by polluted air? Has the air we breathe become so contaminated by soot, gases, vapors, and oil and gasoline fumes that lung cancer is threatening more and more Canadians?”
This is a more chilling suggestion than the one involving cigarettes. Most people can give up smoking: nobody can give up breathing. Depending on his size and physical activity an individual must inhale from eight thousand to sixteen thousand quarts of air a day. Many scientists link this air with the rising incidence of cancer. “It is almost certain that air pollution is one of the main causes,” says Dr. Kingsley Kay. of the Department of National Health and Welfare at Ottawa. A University of Southern California pathologist. Dr. Paul Kotin, who gave lung cancer to mice by having them inhale polluted urban air. asserts bluntly that “air pollutants may be twenty thousand times more potent as a cancer cause than tobacco tars.”
When he visited Toronto in 1956, Dr. Antoine Lacassagnc, of the Pasteur Institute in Paris, commented, “Breathing the air of this city does the equivalent damage of smoking forty cigarettes a day.” Dr. R. M. Taylor, executive director of the National Cancer Institute of Canada, finds the relationship between lung cancer and contaminated air "a logical one."
Just a few weeks ago a special committee on air pollution reported to the Ontario government that the situation in Toronto had become critical. It recommended that a government commission, with widest powers of action, be appointed to look into it. Because, the report said, “air pollution is a most serious health hazard and a major cause of lung cancer and other malignancies.”
The widespread concern about lung cancer, of course, stems from the fact that the disease is killing more and more people. In 1932 it was responsible for 2.1 percent of all Canadian cancer deaths; by 1955 the figure had jumped to nine percent. In the last twenty-five years, the death rate from lung cancer per 100.000 population in Canada has quadrupled.
In trying to find out why, doctors and scicn-
‘•‘•Air pollutants may be 20,000 times more potent as a cancer cause than tobacco tars”
‘•‘•Breathing the air of a city like Toronto does the equivalent damage of smoking forty cigarettes a day”
‘•‘•Nobody knows how many cancer-causing agents are adrift in the air... but hydrocarbons from the incomplete combustion of coal and fuel may be the worst”
‘•‘•The exhaust your car gives out in two minutes can cause skin tumors in laboratory mice”
tists have used two principal methods of research. The first is to test suspected cancercausing substances on laboratory animals. The second is to analyse lung-cancer-death statistics in humans and determine where the cases arc concentrated. They then seek to discover features about the lives of the victims that may be significant, such as their diet, place of residence and vocation.
Both these research methods seemed to prove that the cigarette was at least parti) responsible for lung cancer. Tobacco tar painted on the skin of mice often produced malignant tumors. Dozens of studies showed that the more you smoked the more likely you were to get lung cancer and that as the consumption of tobacco rose so did fatalities from lung cancer.
However, many authorities agree with Dr. W. C. Hueper of the National Cancer Institute, U. S. Public Health Service, when he argues, “You can’t place the entire blame on the cigarette. Too many questions remain unanswered." Why do so many non-smokers develop lung cancer? Why are the victims so often men. so seldom women? (In Canada the sex ratio is tour to one; in some other countries it's much higher.) Why are there such great variations in the lungcancer death rate among urban and rural residents. from country to country, city to city? Among workers in various industries? Among members of various economic groups?
Big-city air is deadlier
Hueper points out that many things besides tobacco consumption have changed in the world since 1920. And any of them might cause lung cancer. Gas. coal and oil consumption have zoomed, motor traffic has multiplied, manufacturing industries have mushroomed and thousands of miles of tar-surfaced highways have been built. Such changes have filled the air with pollutants, many of which are known—or suspected—to cause cancer.
If contaminated air is responsible for lung cancer, the disease should be more prevalent in urban than in rural areas. In Canada, Dr. A. H. Sellars, medical statistician of the Ontario Department of Health, found that the provinces with the highest proportion of urban dw'ellcrs had the highest rate of respiratory cancer. Ontario headed the list; Prince Edward Island was at the bottom. Sellars found that the lung-cancer death rate in such large cities as Toronto and Windsor was well above the Ontario average.
In the large cities of England. Wales and Denmark the lung-cancer death rate is usually tw'ice as high as it is in the rural areas. In a recent year, Canada, with six people per square mile,
had one lung-cancer death per 7,960 people. The United States, with fifty people per square mile, had one lung-cancer death per 6,600. England, with 753 people per square mile, had a lung-cancer death for every 3.200 inhabitants. One British investigator has claimed that there’s a direct relationship between the number of lung-cancer cases in any given area and the number of chimneys per acre.
Perhaps even more startling is the difference in lung-cancer rates in different areas wfithin the same city. In Pittsburgh, many poorer families live in the lower section of town where the air is heavily loaded with the fumes of coal tar, petroleum and arsenic—all established or suspected carcinogenic agents. The skinand lungcancer rate among males of this economic group is double that of males for Pittsburgh as a w'hole. Studies by Dr. Clarence A. Mills of the University of Cincinnati have shown that in cities where soot is heaviest, deaths from lung cancer. TB and pneumonia are highest.
Where do these deadly contaminants come from? Pollution has many sources. Vehicles— with either gasoline or diesel engines—spew out noxious fumes. It has been estimated that Toronto. with half a million cars, is exposed to a billion cubic feet of exhaust fumes a day. Steamships. trains and domestic and industrial oil furnaces foul the air. So do garbage incinerators. Metropolitan Toronto alone burns 700.()()() tons of garbage a year. Additional pollution comes from refineries, brickyards, smelters and other manufacturing plants. The wind carries abrasive dust from tires and highways.
There’s a limit to the amount of dirt the air can absorb without jeopardizing human health. “Some urban areas have already reached a potentially dangerous state." says Dr. Morris Katz, air-pollution consultant to Canada’s Department of National Health and Welfare. "The pollution problem that will result is our top future headache.” says Professor E. A. Allcut of the University of Toronto.
Perhaps the severity of the headache will be lessened if we learn more about the chemical composition of the pollutants and exactly how they attack humans. There are large gaps in our knowledge. However, we do know that the size of the pollutant in the air is all-important. Large particles are screened out by the nasal passage. But tiny particles can penetrate deep into the lung. If they happen to be a cancercausing material they can ultimately irritate the tissue to the point where a cancer results.
Nobody knows how many kinds of cancercausing agents are adrift in urban air. At present. scientists are most concerned about a family of chemical agents named
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Is smog the real culprit of lung cancer? Continued from page 19
“Near highways the lung-cancer rate is twice that of communities far away from the roads”
aromatic hydrocarbons. The most dangerous member of the family is known as 3,4-benzpyrene. The hydrocarbons come from the incomplete combustion of coal and fuel; they pour out of the exhaust pipes of every automobile and truck. Each day in Los Angeles (four times the size of Toronto) an estimated 1,400 tons of hydrocarbons are dumped into the air.
The proof of 3,4-benzpyrene’s danger is both experimental and statistical. Doctors Paul Kotin and Hans I.. Falk of the University of Southern California painted mice with an extract prepared from gasand diesel-engine exhaust. A large proportion developed skin cancer. The doctors then took 338 mice and left them for a year in a chamber filled with synthetically made polluted air. Eighty percent of them developed lung cancer. Among a similar group of mice kept in clean air, only half developed tumors.
Experiments elsewhere have yielded similar results. The U. S. Public Health Service prepared extracts from air samples taken from ten American cities. They caused skin cancer on mice. Dr. Sidney Mittler of the Illinois Institute of Technology found that seventy-six percent of mice painted with an extract made from car exhaust developed skin tumors. He reported that the “amount used on each mouse was the equivalent amount of exhaust produced by letting your car engine idle for about two minutes." When researchers examined the lungs of mice that died of lung cancer after living in polluted air, they discovered that lung areas stained black by soot were the identical areas where human beings develop lung cancer. At present Doctors A. C. Ritchie and G. C. McMillan, McGill University pathologists. are examining a black substance found in the human lung. They report: "We know that it comes from the atmosphere. that it increases with the age of the person, and that it is present in larger quantities in urban than in rural dwellers.”
That 3,4-benzpyrene in the atmosphere is a major factor in causing lung cancer is further suggested by an epidemiological study carried on by Dr. Percy Stocks of the British Empire Cancer Campaign and Dr. John M. Campbell, a London pathologist. They compared the lung-cancer death rate among male smokers and non-smokers in heavily polluted Liverpool, in slightly polluted Chester and Wrexham, and in several rural
areas in north Wales. Liverpool air was found to have eight to eleven times as much 3,4-benzpyrene as the rural air. In every category—non-smoker, light, moderate and heavy smoker—the Liverpool lung-cancer death rate exceeded the rural rates. Liverpool non-smokers succumbed to lung cancer nine times as frequently as rural non-smokers.
Stocks and Campbell say: “Compare the lung-cancer death rate with the population’s total 3,4-benzpyrene intake and you have a remarkable degree of correspondence—so great that 3.4-benzpyrene may be the cancer-causing agent."
These conclusions are endorsed by the U. S. Public Health .Service expert. Dr. Hueper. The rise in lung cancer, he says, follows the rise in consumption of motor and other fuels, the construction of asphalt highways, and finally, the increased production of chemicals and products that give off carcinogenic fumes, dusts and gases to which large occupational groups are exposed. Hueper has published some two hundred papers on environmental cancer and allied topics.
In defense of the cigarette
Hueper takes issue with a fundamental belief of proponents of the cigarette theory: namely that the incidence of lung cancer began to rise with the widespread introduction of cigarette smoking about 1920. “That’s not correct.” he says. “Even before the turn of the century there was a gradual increase in central Europe and it became a matter of serious concern around 1920.” Hueper frequently refers to the study conducted by Doctors J. Herbich and R. Ncubold in four provinces of their native Austria. The per-capita cigarette consumption was the same in each province. Yet in communities along the main highways where the air was polluted by fumes and dust from cars, diesel trucks and asphalt the lung-cancer rate was twice that of communities far away from highways.
A twenty-year study, recently published by the New Zealand Department of Health, also seems to strengthen the case for the defense of the cigarette. Dr. D. F. Eastcott compared the lung-cancer death rate of native-born New Zealanders with that of British immigrants. New Zealanders are much heavier smokers than the British. On the other hand, the British were brought up breathing air polluted in the heavier industrialization of their homeland. The British immi-
grants, Eastcott discovered, faced a thirty-percent greater danger of dying of lung cancer than native New Zealanders.
According to many observers, air pollution may also provide a key to the mystery of why men are more susceptible to lung cancer than women. In the past twenty-five years, the lung-cancer rate for men has skyrocketed; it has gone up only slightly for women. The explanation offered by those who blame air pollution is that men and women spend their lives in different environments. Women spend most of their time in the residential sections of cities or in the green suburbs. Men, on the other hand, may work at jobs where there are known or suspected cancer agents in the atmosphere.
The argument is strengthened by the fact that when men and women spend their lives working and living in the same environment they apparently run the same risk of lung cancer. Male and female employees in the asbestos industry tend to have the same lung-cancer rate.
According to Dr. Hneper's summary the fumes and dusts of the following substances are probably most cancer producing: arsenic, asbestos, chromates, nickel. coal tar, petroleum oils, isopropyl oil (used to make industrial solvents), and radioactive chemicals. Many industries using these substances have taken elaborate measures to safeguard the health ol then; employees. The greatest danger, according to Hueper, is ignorance. “Our knowledge about occupational lung cancers is still spotty," he says.
Some of the studies that link specific industries with lung cancer are impressive. In a large American railway company twenty-five percent of the employees worked at operating jobs. These included engineers, foremen, roundhouse personnel and others exposed to coal, soot and diesel-oil fumes. The non-opcrating employees—seventy-five percent of the railway's total work force—were engaged in clerical, administrative and other chores, far removed from the pollutants. Over a period of several years, medical records revealed that the operating personnel—only twenty-five percent of the force—developed seventy-five percent of the railway's lung-cancer cases.
In Minnesota in 1954, the lung-cancer death rate for all residents was 11.6 per I ()().()()() population. However, among the iron-ore miners of St. I.ouis-Itasca C ounty, the rate was 60.1. In plants where chromium (used in making steel, cutlery, certain inks and paints) is a raw material some workers come in contact with chromium fumes and dusts. After examining the mortality records of such workers in six American chromate plants Doctors Frederick Gregorius and Willard Machle found that lung cancer was sixteen times as common among them as among males in the general population. In England. Dr. Richard Doll followed the health history of 113 men exposed to the dust of asbestos manufacturing for twenty years or more. Several lung-cancer deaths occurred. His conclusion was that the veteran asbestos worker was ten times as likely to succumb to the disease as the males in the general population.
In Deer Lodge County, Montana, a large proportion of the men work at copper smelting. They inhale arsenic dust and fumes. Their lung-cancer rate is 145.7. At the other end of the same state, in Gallatin County, which is predominantly agricultural, the male lungcancer rate is only 5.2.
If man has unwittingly created an environment conducive to lung cancer, is there anything he can do to correct the
situation? This is being studied by experts in several countries who recognize that air pollution has a variety of evil effects. Polluted air may increase the incidence of pneumonia, bronchitis and allergies. It aggravates existing illnesses. A heavy smog (air pollution plus fog) descended on London, England, for five days in December 1952. It killed four thousand people—most of them older people with respiratory and cardiac ailments. Air pollution soils buildings, clothing and furniture. it corrodes paint, metals and stone. It damages vege-
tation. It reduces sunlight intensity, depriving us of health-giving rays and creating hazards for ground and air travel. Dr. Kingsley Kay, of the Department of National Health and Welfare, says flatly: "Airborne filth costs Canada $150 million a year." This does not include injuries to health and fuel wastage due to improper combustion.
In Canada we are only beginning to awaken to the dangers of air pollution. In Ottawa, the health department provides a consultation service for the provinces and municipalities. Dr. E. H.
Tossing, chief of the department’s epidemiology division, is studying 120.000 DVA pensioners to determine what factors—smoking, air pollution, or job history—arc important in lung cancer. He’s also observing the effect of polluted air on a group of chronically ill patients in the Ottawa area. The Ontario legislature has a committee on air pollution. So have the Canadian Manufacturers' Association, the Canadian Standards Association and the Ontario Research Foundation. Industries in the Sarnia area have set up a co-operative research proj-
ect to study air and water pollution. The International Joint Commission has for years been developing methods of cleaning the air in the Detroit-Windsor area. At present, investigations arc under way to determine the extent of pollution in Halifax, Toronto, Hamilton, Winnipeg and Vancouver. Most large communities are organized in some way to deal with the problem of smoke abatement and air pollution.
Smoke abatement is a relatively simple problem that can be handled by local governments if they have proper stall', budget and laws. Other types of pollution — invisible gases and fumes — are much harder to control. For this reason, the Ontario Research Foundation has suggested the establishment of a strong, central anti-pollution agency that would conduct research and loan personnel and equipment to municipalities.
Such an agency, in the opinion of the Air Pollution Foundation, a voluntary U. S. organization, should give top priority to the problem of controlling gasoline and diesel-engine exhaust. (Los Angeles estimates that at least fifty percent of her
pollution comes from vehicles.) The APF makes other suggestions as well. The simplest is that all cars should have their engines properly adjusted: an out-of-tune engine may discharge ten times as much poisonous hydrocarbon as an efficient engine. Another idea is that a method be found of cutting down the (low of fuel while a car is slowing down, to curtail fumes. Perhaps the most important proposal is that all cars be equipped with a catalytic exhaust muffler. The Southwest Research Institute of San Antonio. Texas, claims that this device will reduce hydrocarbon emission by seventy percent or more. The Automobile Manufacturers Association has spent millions of dollars developing anti-pollutant devices. It's possible that some of them will be incorporated in the 1958-model cars.
New York City has shown that locai ordinances can reduce motor pollution. When a car is idling, stopping or starting, there is a heavy hydrocarbon emission. A New York regulation requires bus drivers to shut down their engines if they are going to remain standing at
a terminal for more than three minutes.
What can be done about the lungcancer hazards in specific industries? Obviously, essential industries can’t be shut down. As a starting place. Dr. Huepcr suggests that government, industry and medicine get together on research. “We know too little about the carcinogenic hazards in industry,” he says, and must identify what the cancercausing agents are, how powerful they are, how long they take to work and how they work. Then, he adds, engineers should be able to reduce the cancer hazards to a minimum. As for industries that can’t be made safe for employees, they “should discontinue the production of any product that is not essential to human welfare.”
Each year we spend millions of dollars making sure that the water we drink and the food we eat are pure. If hundreds of scientific studies have any meaning, man's next — and perhaps most crucial — battle against his environment will be the struggle to reclaim the air which he has unwittingly contaminated.