Lead is a naturally occurring metal found in rock and soil and also has many industrial applications. Due to both its natural occurrence and long history of global use, lead is ubiquitous in the environment and is present in air, water and soil as well as in food, drinking water and household dust. Levels of lead in most environmental media have declined significantly over the past few decades due to the discontinued use of lead in paint, gasoline and the solder used in food cans.
Since the phase-out of leaded gasoline and the subsequent reduction of airborne lead, food and drinking water are the primary sources of lead exposure to adults within the general population. In addition to food and drinking water, the ingestion of house dust and soil containing lead can also significantly contribute to the lead exposure of infants and toddlers.
Lead is not permitted to be added to foods sold in Canada; however, due to its ubiquitous presence in the environment, it is present in all foods, generally at very low levels. Lead can enter the food chain through various pathways. For example, plants uptake lead from the soil and airborne lead may also be deposited on their surfaces. Also, fish can absorb lead from water and sediments while other animals may be exposed to lead through the foods they eat.
Lead may also be introduced to foods from the use of lead containing dishware such as lead glazed pottery or lead crystalware. The preparation of foods with water containing lead can also introduce lead to foods. Consuming wild game that has been shot with lead bullets is another potential source of dietary lead exposure.
Health Canada's Total Diet Study measures the concentrations of various chemical contaminants in foods purchased at retail locations in major urban centers across Canada and then prepared as consumed. The food items analyzed represent the typical Canadian diet. This information is then used to estimate the average dietary intake of those contaminants by the Canadian population.
Figure 1 illustrates that the average dietary intake of lead by Canadians of all ages has decreased approximately eight-fold between 1981 and 2000. The primary reason for this decrease has been the discontinued use of lead solder in food cans in Canada in the early 1980s and in most imported products by 1990. Figure 1 also illustrates that since the year 2000, the average dietary intake of lead by Canadians of all ages has remained stable at about 0.1 µg/kg body weight per day. The food groups contributing most to the dietary intake of lead since 2004 are: beverages (which includes beer, wine, coffee, tea and soft drinks), and cereal based foods and vegetables.
Lead has no known function in the human body. Infants and children are most sensitive to the harmful effects of lead because they are undergoing a period of rapid development and they absorb lead more easily and excrete it less efficiently than adults. The most sensitive endpoint of lead toxicity in infants and children is the reduction of intelligence quotient (IQ) score. In adults, the strongest scientific evidence to date suggests low levels of lead exposure may cause a small increase in blood pressure.
In 2011, Health Canada published its Lead - State of the Science Report and Risk Management Strategy. This draft report concluded that although blood lead levels have significantly declined since the 1970's, sensitive adverse health endpoints, such as those noted above, have been associated with the low blood lead levels that are currently present in Canadians. Therefore, additional measures to reduce lead exposure are warranted.
Information about the federal risk management initiatives relating to non-dietary sources of lead can be found in the Proposed Risk Management Strategy for Lead, which was published by Health Canada in 2011.
With respect to lead in foods, Health Canada's Food Directorate has developed the Food Directorate Updated Approach for Managing Dietary Exposure to Lead. As outlined in this document, the Food Directorate continues to work towards reducing dietary exposure to lead to levels that are as low as reasonably achievable (ALARA principle). This strategy focuses on the continued assessment of dietary intake of lead, revising the health risk assessment of lead in foods, identification and control of point sources of lead contamination of foods, and developing risk management recommendations regarding lead.
Health Canada continues to monitor the concentrations of various chemicals, including lead, in foods through its ongoing Total Diet Study surveys and also conducts targeted surveys of lead in specific foods. Additionally, the Canadian Food Inspection Agency carries out monitoring and surveillance work for lead in foods, including those commonly consumed by infants and children.
The Food Directorate is in the process of updating the maximum levels for lead in foods in the Food and Drug Regulations to make them more protective of human health. Where appropriate, the updated maximum levels will be aligned with the maximum levels (MLs) of the Codex Alimentarius Commission (Codex). Additionally, Health Canada's Food Directorate is participating in the working group that is reviewing existing Codex MLs for lead in food based on the results of the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) June 2010 toxicological review of lead.
The levels of lead in foods sold in Canada are generally very low, therefore there is no need to change your food consumption habits in order to reduce exposure to lead. The one exception is individuals that consume game harvested with lead shot, who may wish to avoid this source of food or consume game harvested with non-lead bullets.
Health Canada also recommends that food and beverages are not stored in lead crystalware, and that pregnant women, children and infants are not served food or beverages from these types of dishes. Furthermore, if you purchase glazed ceramic or glass cookware or dishes abroad, be aware that they may not meet Canadian permitted levels for lead and, as a precaution, should not be used to serve food or beverages.
Finally, Health Canada recommends that Canadians consume a variety of foods from different sources and from each food group as described in Eating Well with Canada's Food Guide.