Team Links Cancer Risks to How and Where We Live
 Traditionally, surveillance systems have provided information on the
prevalence of a disease or condition. Although helpful, this kind of system
can't provide clues as to why these rates are higher, nor point to potential
solutions.
Health Canada's National Enhanced Cancer Surveillance System (NECSS)
provides information on geographic and behavioural factors that may influence
the prevalence of disease.
Headed up by Dr. Yang Mao, the NECSS was built by collecting information
from a Canada-wide sample of 20,755 recently diagnosed patients with cancer
and 5,039 population controls. Each individual completed a detailed, risk
factor questionnaire. In parallel, the Environmental Quality Database
was developed, which facilitates the examination of the relationships
between cancer and the quality of air and water in Canada.
Together, this enhanced surveillance system helps the department study
both the influence of environmental factors on cancer in Canada, as well
as behavioural risk factors.
Environment-Related Cancer Surveillance
The geographic component of the NECSS is very important in determining potential environmental risk factors for cancer and creating the potential to reduce the associated health risks. For example, Dr. Mao's team has conducted a study of residential proximity to industrial plants and non-Hodgkin's lymphoma.
Analyses are also underway to examine the association between chlorination disinfection by-products in drinking water and bladder cancer. The surveillance system allows for detailed study of more than a dozen other cancers and chlorination disinfection by-products, many of which have never before been examined anywhere in the world.
Physical Activity and the Risk of Lung Cancer in Canada
Data on risk factors collected through the NECSS has provided
Health Canada with the opportunity to examine the relationship between
physical activity and lung cancer risk in Canada.
The System's questionnaires included information on recreational activity
two years before the interview. Analysis of this data suggested that recreational
physical activity is associated with a decreased lung cancer risk for
both genders. It also found that recreational physical activity had a
much greater protective effect against lung cancer for smokers, and for
those with low or medium body mass index.
Second-Hand Smoke and Breast Cancer
The NECSS has also contributed to the emerging evidence suggesting a
link between second-hand tobacco smoke and breast cancer. A study by Health
Canada scientists showed that passive smoking was associated with more
than a doubling of risk of breast cancer for the pre-menopausal woman.
Risks for post-menopausal women were not as high, but were still elevated.
The researchers observed a relationship between the dose of passive smoke
and cancer risk for all women studied.
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