Hazardous Wastes | The Canadian Encyclopedia


Hazardous Wastes

Waste may be defined as any substance for which the generator or owner has no further use. Hazardous wastes are waste substances whose disposal in the environment could potentially pose hazards to human health, jeopardize natural or agricultural resources, or interfere with other amenities.

Hazardous Wastes

Waste may be defined as any substance for which the generator or owner has no further use. Hazardous wastes are waste substances whose disposal in the environment could potentially pose hazards to human health, jeopardize natural or agricultural resources, or interfere with other amenities. Disposal of hazardous wastes should be carried out in such a manner that the associated threats to people, resources and amenities are acceptable and minimal.

A recent environmental policy development, both internationally and within Canada, has been the formal acceptance of a concept known as the precautionary approach (or principle). This embodies the ethic, long used by scientists in assessing potential dangers and risks, of adopting pessimistic assumptions in assessments of environmental impacts and the formulation of environmental policy as a means of ensuring greater protection of the environment.

Terrestrial Environment
In the 19th century it was realized that WASTE DISPOSAL must take place in a well-regulated and safe manner, if only to control the spread of disease. The ever-increasing variety of consumer goods generates wastes that are becoming increasingly hazardous. It has been estimated that a million people produce 50 000 to 250 000 t of hazardous wastes each year.

Disposal Problems

Standard sanitary landfills and sewage treatment facilities are inadequate for the disposal of many hazardous wastes, particularly those derived from industrial practices. The dumping of untreated hazardous chemicals can have far-reaching effects. The discharge of inadequately treated liquid waste to rivers and streams has created problems for communities downstream, and landfill dumps of waste chemicals have created significant health hazards to people living in their vicinity.

Buried chemicals can produce vapours which can escape to the atmosphere, while liquids, if inadequately contained, can seep into the earth, enter GROUNDWATER and affect drinking water supplies far from the dumpsite. Furthermore, a variety of products and degradation products remain in the environment to enter the hydrologic cycle and be transported through it.

The insidious nature of the effects of low levels of some chemicals in the environment makes it difficult to set safe levels of human exposure. The effects of carcinogenic and mutagenic chemicals may not show up for many years, and often the health defects that do occur cannot be related to a specific cause.


Many hazardous wastes can be treated to render them relatively harmless to humans or to the environment. Such treatments include recycling, physical or chemical reactions, incineration (high-temperature degradation), biological degradation, solidification, deep emplacement and long-term recoverable storage.

Recycling, by far the preferred method for recoverable chemicals (eg, waste oil, solvents), provides viable industries in many countries, including Canada. Some chemicals can be treated chemically to form stable, nontoxic materials; eg, some acids can be neutralized to less hazardous brine or precipitated as insoluble salts which can be landfilled.

Organic chemical wastes can be incinerated in properly designed furnaces equipped with scrubbers so that only carbon dioxide and water vapour reach the air in appreciable quantities. Thus, even persistent chemicals such as polychlorinated biphenyls (seePCBs) can be safely destroyed in well-regulated installations if the incineration time and temperature are sufficient for total decomposition and if adequate checks are made on the formation and emission of recombinant products. Other hazardous chemicals normally emitted from chimneys (eg, fly-ash, other fine particles, acids and alkalis) can be electrostatically precipitated or scrubbed out.

Many industries treat biodegradable liquid wastes with bacteria before discharge to surface waters. Heavy metal wastes (eg, electroplating liquors) can be incorporated into a concretelike mass which resists leaching from burial sites. In some areas, waste liquids (eg, brine) can be ejected into permeable underground formations overlain by impermeable rock (deep-well injection).

There is a distinct worldwide shortage of proper hazardous waste treatment facilities. In Canada, a milestone was reached 11 September 1987 when North America's first comprehensive integrated hazardous waste treatment facility was opened at Swan Hills, Alta, with the full support of the local people. It is a state-of-the-art facility, capable of treating and safely disposing of most hazardous waste produced in the province. Other provinces are attempting to set up additional facilities to handle the estimated 5.9 million t of hazardous waste generated in Canada each year.

Radioactive Wastes

No practical detoxification methods are yet available for some kinds of hazardous wastes such as radioactive material (although it can be incorporated into a matrix such as glass to restrict its release to the environment). Low-level radioactive wastes can often be disposed of safely in shallow trenches on land or can be dumped in the ocean with acceptable risks to human health.

High-level radioactive wastes such as spent fuel rods are not amenable to such disposal and can either be stored temporarily for future treatment (eg, reprocessing for the recovery of fissionable plutonium) or placed in permanent underground repositories, as is likely to be the case for spent nuclear fuel from Canadian reactors. Sites for such repositories must be selected with the utmost care, taking into account all potential pathways of leakage which might result in human exposure and all potential disturbances to sites which might threaten their integrity, such as tectonic activity or inadvertent human activity.

Hazardous Waste Management

Although most wastes can be treated for safe disposal, many are not currently so treated (because of short-term economic considerations) where regulatory requirements allow such discretions. The costs of proper waste treatment are seldom included in the costs of production unless this is a regulatory requirement. However, unless such requirements are applied uniformly in an international context, countries introducing more stringent environmental protection regulations may be placed at an economic disadvantage in export markets. Even where legislation to eliminate unsafe practices exists, illegal disposal can still remain a problem. Increased attention to the enforcement of regulations is thus essential.

Marine Environment

Various views are held on the use of the ocean as a receptacle for wastes. Some regard the ocean as "waste space" that could be used for waste disposal because of its extensive capacity to assimilate materials without deleterious effects. Others feel strongly that the ocean environment should be preserved in as pristine a state as possible because any major disturbance of the vast and complex oceanic ECOSYSTEM will be difficult to reverse. The former view reflects the historical situation when the global population and urban communities were smaller and scale of anthropogenic activities (ie, produced by humans) was much less than that of today. The latter view is now becoming dominant and is consistent with the increased adoption of the precautionary ethic.


Marine Sources
Deliberate dumping of material into the marine environment is generally governed by the 1972 International Convention for the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, commonly referred to as the London Dumping Convention. Until 1997, the convention specified a "black list" of substances (eg, organohalogen, mercury and cadmium compounds, persistent plastics, oils and high-level radioactive wastes) which may not be dumped into the marine environment except as trace amounts in otherwise acceptable materials. A further "grey list" defines potentially hazardous substances (eg, arsenic, lead, copper and zinc compounds, cyanides, fluorides and pesticides) which require special precautions in evaluating their suitability for dumping and in the procedures used for dumping at sea.

In 1997, amendments made to the London Convention replaced the black and grey lists with a list of restrictive list of materials that may be considered for ocean disposal subject to prior evaluations of their effects on the marine environment and the availability of alternative avenues of treatment, recycling or disposal.

The discharge from ships of petroleum, noxious liquids carried in bulk, harmful substances carried in packaged form, sewage and garbage is covered by the international convention for the Prevention of Pollution from Ships, 1973 (MARPOL 73/78). MARPOL is a global convention with a comparatively large number of contracting parties (95, including Canada) and applies to the vast majority of the worlds shipping fleet tonnage (some 93%).

The international convention on Oil Pollution Preparedness, Response and Cooperation, 1990 (OPRC 90) was formulated in response to the frequency and severity of oil spills in the marine environment. Canada, through amendments to the Canada Shipping Act in 1993, ratified its accession to the OPRC 90 in 1994 and the convention came into force in May 1995. OPRC 90 deals specifically with oil pollution preparedness and response and its contracting parties are examining the possibility of expanding its terms to cover hazardous chemicals.

Direct and indirect (ie, by way of freshwater discharges) introductions of substances to coastal waters have resulted in several instances of metallic and organic chemical contamination of nearshore areas, particularly within embayments that have restricted water exchange with offshore areas. Various Canadian East Coast, West Coast and Arctic bays and fjords have been affected in this way.

Large-scale contamination, however, is difficult to detect for many substances because of the large assimilative capacity of the ocean itself and because of large marginal sea areas (eg, the Gulf of ST LAWRENCE; Bay of FUNDY). Anthropogenic activities on land and continental runoff represent respectively, the predominant source and predominant avenue of transport of materials entering the ocean. The cumulative effects of the introduction of contaminants are evident in the oceanic incidence and distribution of some heavy metals, radionuclides and artificial organic compounds such as PCBs. It should be stressed that the real dangers posed by the release of contaminants to the environment can be judged only in the context of adverse effects on human health, environmental resources and amenities rather than the mere presence of substances.

Precautionary Approach

A more comprehensive approach to hazardous waste management incorporates 3 distinct principles: justification of practices; limiting risks to human health and the environment; and minimizing detriment to the extent reasonable in the context of socioeconomic circumstances. Justification requires that the potential benefits of the potential production and use of some new substance are assessed against the detriments (eg, the risks to human health and the likely scales and risks of environmental damage) in order to determine that there is an overall net benefit to be gained from investment in the industry. Safe limits to the exposure of humans to the products and wastes disseminated from the industry need to be established and regulatory action adopted to ensure that releases of hazardous materials to the environment do not violate these limits irrespective of the route of exposure. Finally, all alternative options for the production, transport, dissemination and disposal of hazardous products and wastes should be evaluated to ensure the selection of those that minimize the exposures to the extent commensurate with technical, economic and sociopolitical conditions. In the field of radiation protection these 3 principles are applied to practices and are referred to respectively as justification, compliance with dose limits and optimization.

Banned Substances

The current trend towards the adoption of greater precaution has resulted in moves to reach an international agreement to ban, or phase out, the production of certain classes of substances such as some described as "persistent organic substances." These are substances determined to have the attributes of toxicity, persistence and the potential to bioaccumulate. Many countries have already banned the production of DDT and PCBs, but the number of substances so banned can be expected to increase if the contemporary trend in international negotiations continues.

Disposal Problems

The oceans have long been used, both deliberately and accidentally, for the disposal of human and industrial wastes. Potentially deleterious effects of hazardous wastes disposed of into the marine environment include hazards to human health (eg, exposure of bathers to pathogens), hindrance with legitimate uses of the sea (eg, fishing), degradation of the quality of sea water, making it less suitable for recreation, desalination or other uses, and less tangible reductions in the aesthetic attractiveness of the ocean environment.

Contamination Sources

The main types of deliberate waste disposal into the ocean include direct discharge from land through outfalls or other pipelines, dumping from ships and other marine platforms, and incineration on, or liquid discharges from, ships or marine and coastal platforms. Waste materials discharged on land or into freshwater reservoirs (rivers and lakes) may also reach the sea, indirectly through land runoff.

Wastes routinely discharged by pipeline or outfall into the coastal zone in Canada include sewage and wastes from metal and oil refining, foodstuff processing, and pulp and paper production. In Canada and other coastal states, heat is also discharged to the sea in cooling water from power utilities and from other industrial facilities.

Another avenue for the introduction of waste materials found in the ocean is the atmosphere. Volatile substances, or substances with significant vapour pressures, derived from terrestrial activities can enter the atmosphere and be subjected to short- or long-distance transport, frequently resulting in large-scale contamination of land and ocean environments. An example of such large-scale contamination is that which occurred during the era of atmospheric nuclear weapons testing in the 1950s and 1960s. More recent concerns have centered around the long-distance transport of relatively volatile organic compounds that as a result of a global "distillation" process have a tendency to accumulate in cold regions such as the Arctic.

Land Sources

Until very recently, discharges into the ocean from land were not governed by international agreement in the same way as ocean dumping. The major regional convention covering discharges of waste materials from land is the Paris Convention, covering the eastern North Atlantic and adjacent coastal areas, to which most western European countries are signatories. Canadian legislation governing discharges of material from land includes the Fisheries Act, the Canadian Environmental Protection Act, the Navigable Waters Protection Act and the Arctic Waters Pollution Prevention Act (seeENVIRONMENTAL LAW).

In 1985 a major step was taken in formulating international agreement on the marine pollution prevention from land-based discharges with the formulation, under the aegis of the United Nations Environment Programme, of an Agreement for the Protection of the Marine Environment Against Pollution from Land-Based Sources. This agreement is commonly referred to as the Montréal Guidelines, after the city in which it was finalized. It did not result in much enhanced multilateral attention to problems posed by contaminants introduced through discharges to the marine environment.

In late 1995, primarily as a result of the recommendations adopted by the UNCED in 1992, a further international agreement, referred to as the Washington Declaration, was reached. This agreement incorporates a Global Programme of Action for the Prevention of Marine Pollution from Land-Based Activities. It is more comprehensive than the Montreal Guidelines, as reflected in the use of the term "activities" rather than "sources." The agreement requires states (including Canada, as party to the agreement) to develop "National Programmes of Action" to prevent, reduce and control pollution of the marine environment from land-based activities, including not only through the release of contaminants but also through physical alterations to coastal areas and river drainage basins.

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