1. Introduction

1.1 - Sources and effects of mercury

Mercury^{Footnote 1} is a toxic substance under the Canadian Environmental Protection Act. Mercury occurs naturally in the Earth’s crust and can enter the environment as a result of natural processes such as volcanic activity, erosion and forest fires. It can also be released into the environment through human (anthropogenic) activities such as the burning of coal, the extraction of metals from ore and the use and disposal of products containing mercury. Natural sources account for roughly 60% of the mercury deposited in Canada each year (Environment and Climate Change Canada, 2016). Industrial and other human activities account for the remaining 40% of annual deposits.

Mercury moves through the environment in complex ways over decades. Once in the environment, mercury cycles between air, water, soil, plants, and animals. Because elemental mercury (that is, mercury in its pure form) evaporates, it can move easily through the air, ending up thousands of kilometers away from where it was first released; this makes it a global concern. For example, the vast majority of mercury from human activities deposited in Canada originates from other countries.  In addition, mercury deposited from both natural and anthropogenic sources can be re-emitted by natural processes and then end up in the atmosphere again. Scientists are still working to determine how much the movement of mercury is affected by climate change. All of these factors affect the levels of mercury in Canada’s environment.

Once in the environment, mercury can be converted into various forms, including methylmercury. Methylmercury is a highly toxic compound that accumulates in living organisms, especially animals at higher levels of the food chain. Levels of methylmercury in the environment vary due to human activities and natural factors in the environment such as temperature, acidity, presence of bacteria, and organic matter. Most mercury released to the environment directly from human activities is in its inorganic form, and naturally turns into methylmercury under certain environmental conditions.

Human activities can change environmental conditions, making it more likely that methylmercury will form. Climate change and the acidification of waterbodies are thought to be two of the biggest influences increasing the rates of methylmercury formation. It is the amount of methylmercury available for uptake that drives mercury levels in animal species and not emissions alone.  Mercury levels in the environment may still be changing in certain areas because of the complex way that mercury cycles in the environment. For this reason, a direct link between the deposition of anthropogenic emissions and mercury levels in the environment and in animals is not always clear.

Mercury poses significant risks to Canada’s environment and the health of Canadians. High levels of mercury in the environment can harm wildlife and ecosystems. Humans are most often exposed to methylmercury by eating fish and sea mammals. Methylmercury affects the central nervous system and is particularly damaging to fetuses, infants, and young children, who are vulnerable due to their developing nervous systems.   

1.2 - Government approach to mercury risk management

Over the last 50 years, the Government of Canada has used different risk management approaches to tackle the risks created by releases of mercury including regulations, pollution prevention plans, codes of practice and national guidelines.

In 2009, the Commissioner of the Environment and Sustainable Development (the Commissioner) published a review of federal action on toxic substances. The review noted that there was no consolidated risk management strategy for mercury and that “departments lack a systematic process for periodically assessing progress made in managing the risks [of toxic substances such as mercury]”.

In response to this review, Environment and Climate Change Canada and Health Canada committed to conducting “substance-based performance measurement” for toxic substances. This kind of measurement looks at the outcomes of the actions taken to deal with the risks of a substance, including looking at levels of the substance found in people or the environment. Through this assessment, the government can determine if it has made progress to reach its risk-reduction objectives.

In 2010, the Government of Canada published the Risk Management Strategy for Mercury (the Strategy) (Government of Canada, 2010a). The Strategy reviewed federal and international actions up to 2007, which were focused on managing the risks posed by mercury, and outlined planned actions to address ongoing risks. The Strategy noted that, between the 1970s and 2007, the amount of mercury entering the Canadian environment from industrial releases was reduced by approximately 72 tonnes (91%). Additionally, it found that more science was needed to help manage risks from mercury. This included monitoring to improve our understanding of the movements and changes in mercury levels and the chemical forms of mercury in the environment. The Strategy also showed that more needed to be done to reduce the human health and environmental risks of mercury.

Accordingly, the Strategy proposed new risk management actions the Government of Canada could take to deal with non-industrial sources such as products and waste containing mercury. It highlighted that Canadians would benefit from actions taken to reduce mercury at the North American and global levels since most of the mercury deposited in Canada (97%) comes from other countries.

Following publication of the Strategy, the Government has continued to move forward with both domestic and international actions to further reduce mercury. The current report assesses whether progress has been made in achieving the Strategy’s main objective of protecting the health of Canadians and their environment from the harmful effects of mercury by minimizing and, where feasible, eliminating anthropogenic^{Footnote 2} mercury releases. The following sections provide the status of emissions and releases of mercury from human activities, outlines trends in environmental monitoring data and human biomonitoring data, and discusses how well the different actions taken by the Government of Canada to manage the risks of mercury have performed overall.