Avoiding exposure is the most fundamental preventive advice that can be given to patients.

We likely arm our children with the best possible protection against cancer by instilling healthy habits during childhood.

The patients to target specifically include men and women who are considering having a child, pregnant women (and their partners) and the parents of infants and very young children.

Healthy Milk, Healthy Baby: Chemical Pollution and Mother's Milk is a Natural Resources Defense Council web page devoted to breastmilk contaminants with practical advice and information.

Personal Prevention

Cancer

Improvements in childhood cancer survival are testament to important strides made in treatment and cure. However, prevention is still a preferable goal since cure does not come without suffering on the part of the individual child and family.

Preventing cancer is an immense challenge given our relative inability to pinpoint precise causal factors, particularly for childhood cancers. We also have to acknowledge that only a small fraction of chemicals and substances has been adequately tested for carcinogenicity.

Finally, as stated before, cancer is described as a multifactorial disease involving both environmental exposures and genetic factors. For that reason, it is often emphasized that cancer is largely preventable. The fact that etiology is undetermined for most childhood cancers means, however, that there are few, if any, specific strategies clinicians can offer patients to reduce the risk of cancer in their children.

Based on the existing evidence for risk factors in childhood cancer, avoiding exposure is the most fundamental preventive advice that can be given to patients.

The patients to target specifically include men and women who are considering having a child, pregnant women (and their partners) and the parents of infants and very young children. The clinician might advise these patients to take a prudent approach and avoid exposures to some suspected risk factors such as cured meats, unnecessary x-rays and a variety of chemicals including pesticides, solvents and paints.

It is apparent that children may be more susceptible to radiation-induced leukemia as there is a peak of leukemia incidence about five years after exposure. Where there is potential hazardous workplace exposures, clinicians may be important advocates assisting patients in reducing exposure by changes to the work site or modification of duties.

Research is indicating that other behaviours may reduce the risk of pediatric cancer. For example, a large, international collaborative study of pediatric brain tumours suggests that the risk of childhood brain cancer was significantly reduced when mothers took prenatal multi-vitamin supplements for two or more trimesters of their pregnancy.100,101

The finding that breastfeeding is correlated with significantly decreased risk of acute leukemias in childhood, likely due to the immune-stimulating effects of breast milk, provides yet another reason that breastfeeding should be vigourously supported as the optimal method of infant feeding.101,102

Our knowledge of the links between lifestyle choices and cancer prevention pertains mainly to adults. However, we likely arm our children with the best possible protection against cancer by instilling healthy habits during childhood. For example, there are consistent findings that high consumption of fruits and vegetables, moderation in red meat, fat and alcohol intake and regular exercise and maintaining a healthy body weight are all cancer-protective strategies.102

Although most types of cancers are quite difficult to link to the specific causal exposures (and do not directly affect children), there is still good reason to prevent exposure to carcinogenic substances at the youngest ages possible.103 Clinicians and parents should therefore ensure that a child's exposure to known carcinogens such as environmental tobacco smoke, asbestos and sunlight are minimized in order to reduce the risk of developing cancer in adulthood.

Environment Canada provides forecasts of the daily ultraviolet (UV) indices for selected Canadian cities.

Health Canada's It's your Health series includes the document Preventing Skin Cancer - It's Up to You.

The Canadian Dermatology Association Web site includes useful resources, such as Sun Safe - Tips for Parents and Teaching Pre-schoolers SUNSAFE Play, Everyday! - Tips for Daycares.

Immunological Effects

Research on immune system effects in people from environmental exposures is clearly in its infancy. The number of substances known to be immunotoxic is relatively small, but may only represent the proverbial tip of the iceberg. As such, personal prevention is difficult to achieve. Avoiding certain exposures is virtually the only advice that can be given to patients.

As with cancer, the patients to target specifically include men and women who are considering having a child, pregnant women (and their partners) and the parents of infants and very young children. The clinician might advise these patients to take a prudent approach and avoid exposures to the few risk factors for which evidence of immunotoxicity is accruing.

In particular, people are well advised to avoid certain practices such as:

• Use of pesticides, especially those that are sprayed and/or applied indoors. Spraying and indoor application are both associated with greater exposure of pesticides to humans and pets.
• Consumption of sport-caught fish (especially in the Great Lakes region), which is associated with much greater intake of persistent, bioaccumulating, biomagnifying contaminants and, therefore, is not advised for women in their childbearing years, nor children under fifteen. Others should, at a minimum, follow the provincial guides to sport fish consumption to determine which are the least contaminated fish and appropriate ways to prepare such fish. They should also be mindful of special advisories that notify the public of unusual episodes of contamination. (For example, see the Ontario Ministry of the Environment for fish consumption guidelines and advisories.)

Although there has been increasing evidence of the presence of POPs in breast milk, breastfeeding is still to be advocated as the optimum way to nourish babies since, by what science knows so far, the benefits of breast milk far outweigh the risks from exposure to contaminants in breast milk.104,105

Primary Prevention

Personal prevention represents only one aspect of reducing cancer risk in children. Clearly, when exposures to carcinogens and immunotoxins in the environment most often occur unknowingly and involuntarily, we should strive for greater focus on primary prevention. Specifically, government policies and standards that are informed by current, comprehensive testing of environmental agents will ultimately be the most effective strategy for protecting children from cancer and immunotoxic exposures.

This includes a strong government stance and action to reduce POPs, for instance, in the environment internationally. In the wake of the report of the House of Commons Standing Committee on Environment and Sustainability that made numerous recommendations to reduce pesticide use in Canada, there has still been little substantial action to further those recommendations.

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