Looking for the Bad Apples; Canada Sorts Through Its Toxic Legacy

The government wouldn’t let toxic chemicals which could harm us be used in daily life. That’s one common assumption. Other people assume that there is no process in place to track and assess the thousands of chemicals in our daily lives. Neither assumption is correct.

by Delores Broten

Behind the scenes for the last 5 years, Health Canada and Environment Canada, with the sometimes vigourous advice of environmentalists from a dozenorganizations across the country, have been working to develop a method to revisit all those grandfathered chemicals. They are looking for those which harm humans or the environment. The project is called categorization.  

The government scientists have found thousands of chemical substances which require a careful second look because they are toxic and persistent. 

In 1999, the Canadian Environmental Protection Act (CEPA 99) required the Ministries of Health and Environment to categorize over 23,000 substances for those Canadians were most exposed to, and for those that were persistent, bioaccumulative and “inherently toxic” to humans or other life. 

The 23,000 substances – chemicals, compounds, metals and mixtures – were listed on the 1989 Domestic Substances List (DSL), a list of substances that were used in Canada between 1984 and 1986. Most of these substances have never been examined for their toxicity. 

The 8,000 to 10,000 substances introduced into Canada after 1987 are subject to screening for toxicity and hazard by the New Substances Program, run jointly by Health Canada and Environment Canada. 

CEPA 99 gave Health Canada and Environment Canada 7 years to examine the chemicals which had crept into our lives over the last century. This daunting task has never before been attempted anywhere in the world and must be completed by September 17, 2006. 

Despite its pioneering nature, the categorization requirement is only a sorting process: it will indicate which of those substances in use in Canada in 1986 should be more thoroughly examined for their toxic impact on Canadians or the environment. 

The determination of whether a substance meets the strict requirements to be declared “CEPA Toxic” usually requires a two to three year process. The government then has the option to promote voluntary controls such as labeling or recycling, or to regulate the substance’s use and release. Regulation is rarely used until all possible voluntary efforts are exhausted, which sometimes takes up to 15 to 20 years. 

Substances from the CEPA 99 categorization which are found to be persistent, bioaccumulative and inherently toxic to humans or the ecology will be carried forward to these further assessment processes. The two Ministries approached their CEPA-imposed categorization task in different ways, with both of them finalizing their approaches now, in the fall of 2005. It has taken 6 years to come up with systems for categorization and some preliminary lists on substances in use in Canada in 1986. Both departments stress that other “feeders” can trigger a government response to a toxic substance, such as important emerging science, bans or listings from other jurisdictions, and public nomination.

Health Canada 

Health Canada has developed a set of “tools” or schemata to sort the substances: the Simple Exposure and the Simple Hazard tools, and the Complex Exposure and the Complex Hazard tools. It expects that the complex assessment tools will speed up the health risk assessments after the categorization exercise is complete in September 2007. Health Canada says it may act on some substances before that date. 

First, Health Canada screened all 23,000 chemicals on the DSL for their potential for human exposure, mainly by quantity and a rough cut at current usage. They also looked at obvious health impacts, based on the evidence from other agencies such as the US EPA. They included substances forwarded from Environment Canada which were persistent and/or bioaccumulative but not inherently toxic to nonhuman organisms. 

This produced the Maximal List of substances, Health Canada’s priorities for further assessment. The complex tool evaluations will be then applied to prioritize the Maximal List in preparation for further work after 2006. 

The Complex Hazard tool includes a hierarchy of evidence from the international literature, either actual data or computer models, with a conservative bar for carcinogenicity, genotoxicity, reference or regulatory values from other jurisdictions, developmental, reproductive, long term, short term and acute (lethal) toxicity. 

The Complex Exposure tool develops models of exposure scenarios for different ages and occupations of Canadians, based on the substance’s chemical and physical properties and bioavailability, and on the potential use of the substance in “sentinel products” such household cleaners or cosmetics. Unfortunately, it does not incorporate the significant role of house dust in children’s exposure. 

As of April 2005, Health Canada had prioritized 272 substances – those with High Hazard and Greatest or Intermediate Potential for Exposure – for Screening Health Assessment, along with another 473 substances with the Greatest Potential for Exposure, 98 Intermediate Potential for Exposure which were Persistent or Bioaccumulative, and 289 substances with Intermediate Potential for Exposure where persistence or bioaccumulation are unknown. 

These numbers will change. Health Canada is asking industry for more information on many substances, hoping that some of them can be deleted from this heavy future workload because their use is contained so that Canadians are not exposed. Notably the Ministry is taking the position that if industry does not provide the information needed, the substance will move forward through the complex and long drawn out assessment system. Health Canada says they are hoping that process will take no more than 3 to 5 years, using their new assessment tools developed for categorization. 

Environment Canada 

Environment Canada started their task by grouping the 23,000 compounds on the DSL into four groups of substances: 

• Organics, containing carbon (50% of the list) 

• Inorganics, such as metallics (10%) 

• Polymers (20%) and 

• UVCBs, short for Unknown or Variable Composition, Complex Reaction Products, or Biological Materials, (20%). This includes such innocuous mixes as flour and pectin but also complicated mixtures and heavy metal containing biologicals, natural oils with pesticidal properties, and quaternary ammonium compounds. 

The ministry began by screening these groups for their persistence or bioaccumulation, according to some fairly standard criteria. (See The Definitions) 

However, the process quickly hit difficulties, which to date has meant lists of thousands of inadequately and pos sibly unreliably characterized compounds. 

First, there just wasn’t much information available. Environment Canada says that, for example, of approximately 11,500 organic substances on the DSL, only one fifth had any study data. Further, only three quarters or less of this shockingly meager data haul was of “acceptable quality.” 

Environment Canada filled the gaps in several ways: 

• Like substances were grouped and categorized together 

• Structural models called QSARs (Quantitative Structure Activity Relationships) were relied on extensively, as were other forms of 

• Analogue modeling and, in thousands of cases, 

• Informed expert judgment. 

As of April 2005, Environment Canada had discovered 3,438 substances out of the original 23,000 on the DSL which are persistent and/or bioaccumulative and toxic to the environment — “inherently toxic to non-human organisms.” 

Environment Canada did not screen polymers and UVCBs, 40% of the DSL, for their persistence and bioaccumulation, but moved instead directly to an ecological toxicity assessment (e.g., aquatic toxicity only.) 

The structure of the system required Environment Canada to pass to Health Canada those substances which were persistent or bioaccumulative but not ecologically toxic for assessment for human toxicity. But Environment Canada has not assessed 40% of the DSL for its persistence or bioaccumulation, so those compounds that are not toxic ecologically sit in a kind of limbo. Health Canada now has to choose whether to go ahead and assess the human toxicity of the entire batch. 

As for the path forward, Environment Canada’s prediction in June 2005 was that it will take until 2025 to process the thousands of persistent bioaccumulative and ecologically toxic substances uncovered by categorization. 

It is hard to be critical about such a monumental task. The Health Canada team is obviously proud of the fact that their work provides a model for international evaluation programs. Environment Canada points out that the problem of these previously unevaluated chemicals belongs to the industrial world, and Canada has shouldered more than its share of the burden. 

Nonetheless, some gaps, serious concerns, and potential issues have been noted by the few environmentalists monitoring the process. 

Excluded categories 

Genetically modified organisms were not included in this exercise, since they come under the Ministry of Agribusiness. 

Neither Environment Canada nor Health Canada looked at combinations of chemicals and their synergistic effects. This is an emerging science which admittedly would be difficult to model at this point in time. However, a precautionary approach would try to take these interactions into account. 

Similar but much more troubling is the neglect, by both Ministries, of the breakdown products of these substances. Environment Canada did include the various stages of metal-based substances and based some of its work on the component “pieces” of complex polymers. Both ministries state that they did not have time or resources to categorize or consider degradation products of the substances. This leaves a gaping hole in the reliability of the entire exercise. 


The relationship between Health Canada and Environment Canada, judging from the issues around polymers and UVCBs, has not been the efficient and cooperative one which Canadian taxpayers deserve in this important public and environmental health initiative. 

Old Usage Information 

Almost all the volume of use information is based on 1986 data, although Health Canada did bring in some experts to eyeball the lists and tell them about new uses. Both ministries emphasize substances which are no longer in use, and thus out of categorization. There does not seem to be a corresponding diligence to look at new and expanded uses of substances over the last 20 years of technological and economic expansion. 

Narrow focus on toxicity 

Perhaps the most egregious problem, and one which may even be in contravention of the instructions in CEPA 99 to consider toxicity to “non-human organisms,” is Environment Canada’s refusal to look at any other toxicity data than aquatic, because, the Ministry explains, international standards are based on aquatic toxicity

Further, Environment Canada states that they prefer to consider only acute toxicity (immediate deadliness) because more information is available and chronic toxicity studies tend to be less reliable. 

A focus on acute toxicity means that Environment Canada has excluded chronic toxicity such as hormone disruption or carcinogenicity to wildlife. Environment Canada did pass substances with information on mammalian toxicity on to Health Canada, who considered all toxicity tests in their Complex Hazard tool. However, Health Canada also did not consider endocrine disruption as a toxicity endpoint, despite the enormous strides made in this scientific knowledge in the last decade. 

Persistence and Bioaccumulation 

Environmental organizations consider that Health Canada also is not following CEPA 99’s instructions, which clearly call for a list of those substances with greatest potential for exposure and also substances which are persistent or bioaccumulative. Instead, Health Canada is pre-screening the substances. The environmentalists want the lists developed before chemicals are winnowed out, because it may be necessary to backtrack in the future. The toxics activists also want a list of POPs (Persistent Organic Pollutants) to aid in work around the United Nations POPs Treaty. 

Health Canada is adamant that persistence and bioaccumulation are frequently irrelevant for human health assessment, and proudly declares that, by assessing the human health hazard of all high exposure substances on the DSL, they have gone beyond the requirements of CEPA 99. The environmental groups think that evidence such as the recent studies of industrial chemicals in our bodies should not be ignored just because there is no current evidence of harm to human health. 

Expert Judgment 

A toxicologist working for the environmental groups has found that, in many cases, only some members of classes of chemicals, all of which are considered likely to be carcinogens, have been included in the Maximal List. 

Worst of all, the vast majority of these substances have little or no actual experimental data associated with them for health effects, persistence, or bioaccumulation. They are largely being categorized through the use of models, analogues, and informed “expert judgment.” In most cases, the only source of any data is the industry using the substance. 

Despite the flaws, some glaring, some inescapable, the categorization task is long overdue, and shows a willingness to grapple with the toxic past which is a first among the industrial nations. Canadians have a right to be proud of the effort. The results show that the task justifies the means. 


[From WS September/October 2005]

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