27 August 2009
HC Pub: 8368
ISBN: 978-1-100-13375-1 (print version)
ISBN: 978-1-100-13376-8 (PDF version)
Catalogue number: H113-5/2009-8E (print version)
Catalogue number: H113-5/2009-8E-PDF (PDF version)

This page is a summary of the consultation document. If you would like to comment, please request the full consultation document.

To obtain an electronic copy of the document, Re-evaluation Note REV2009-08, Lindane Risk Assessment, please contact our publications office.

Should you require further information, please contact the Pest Management Information Service.

Summary

Table of Contents

• Background
• Results of the Lindane Risk Assessment
• What Is Lindane?
• Health Considerations
• Environmental Considerations
• Measures to Minimize Risk

Background

From 1999 to 2001, Health Canada's Pest Management Regulatory Agency (PMRA) conducted a special review of agricultural products containing lindane, most of which were used as a seed or soil treatment to protect crops. The PMRA completed its assessment of occupational risk in October 2001, concluding unacceptable risk to the health of workers exposed to lindane during seed treatment and planting. The phase-out of lindane use was communicated in Re-evaluation Note REV2002-02, Update on the Special Review of Lindane and the Status of Lindane Registrations. All registrants of lindane seed treatment products, except Crompton Corporation (now Chemtura Corporation), chose to voluntarily discontinue sales of their products and the registrations expired by the end of 2004. The Crompton registrations were suspended.

Crompton requested a hearing to examine the PMRA's decision. In 2005, a Board of Review reported its findings to the Minister of Health and recommended reconsidering aspects of the occupational risk assessment. To address the issues raised by the Board and to complete the re-evaluation of other health and environmental risks associated with the use of lindane pesticides, the PMRA initiated a new review and requested data and risk mitigation proposals from former registrants of lindane products and other interested parties.

Re-evaluation Note REV2009-08, Lindane Risk Assessment, presents the science evaluation of lindane with respect to pest control products that were registered in Canada as of 2001, taking into account new data and proposals from some former registrants for mitigative measures relating to the application directions of former seed treatment products. The PMRA requested comments from former registrants of lindane, including Chemtura Corporation, on the April 2008 draft of the document. Chemtura provided additional information on a manufacturing process for technical lindane and alternative perspectives on the toxicity and exposure studies on which the health risk assessment is based. The PMRA has taken Chemtura's comments into account and is publishing Re-evaluation Note REV2009-08, Lindane Risk Assessment, for public comment with a 60-day comment period. Please forward all comments to Publications.

Results of the Lindane Risk Assessment

After a thorough assessment, the PMRA finds that the pesticide lindane poses unacceptable risks of harm to human health and the environment. This assessment confirms an earlier decision by the PMRA to withdraw all pest control products containing lindane from use in Canada, either by discontinuation or by suspension under the authority of the Pest Control Products Act.

Health Canada's pesticide re-evaluation program considers potential risks to ensure registered products meet modern standards established to protect human health and environment. Re-evaluation draws on data from registrants, published scientific reports, information from other regulatory agencies and any other relevant information available. In the case of lindane, an evaluation of available scientific information found that, under the proposed conditions of use:

• the risks to human health and the environment do not meet current standards and cannot be mitigated to render them acceptable.

What Is Lindane?

Lindane is an organochlorine insecticide that was used to control a broad spectrum of insect pests on a wide variety of sites. Under international scrutiny, and as a result of its widespread occurrence and persistence in the environment, most uses of lindane were discontinued in Canada by 2002, including use on greenhouse ornamentals, livestock, terrestrial food and feed crops, structures, outdoor ornamentals and turf.

The PMRA's assessment of the occupational risk of lindane addressed the seed treatment uses of lindane registered as of 2001. At the time, seeds were coated with lindane using dry and liquid seed treatment equipment by farmers and farm workers on-farm and by applicators at commercial seed treatment facilities.

This current risk assessment considers uses that continue to be supported by some former registrants, including:

• wireworms on cereal crops (barley, oats, rye and wheat);
• flea beetles on oilseed crops (canola and mustard); and
• root maggots, seedcorn maggots and wireworms on field crops (corn, beans, soybean and peas).

This risk assessment also takes into account a new, more restricted use pattern, including application in closed systems, as proposed by former registrants. The PMRA reconsidered the original data, completed the human health risk assessment in areas not finalized in the previous evaluation (for example, carcinogenicity) and finalized the environmental risk assessment.

Health Considerations

Exposure to lindane may occur through diet (food and water) and when treating seeds or handling treated seeds. When assessing health risks, two key factors are considered:

• the levels at which no health effects occur; and
• the levels to which people may be exposed.

The dose levels used to assess risks are established to protect the most sensitive human population (for example, children and nursing mothers). Only those uses for which exposure is well below levels that cause no effects in animal testing are considered acceptable for continued registration.

An acute overexposure to lindane can produce a variety of symptoms in animals and humans. Symptoms may include nausea, exhaustion, convulsions or seizures. Health effects in animals exposed daily to lindane over long periods of time included effects on the liver, lung, kidney, spleen, thymus and testes. There is suggestive evidence that lindane is genotoxic and causes cancer in animals. There were also indications that lindane caused damage to the central nervous system and altered hormone levels in developing animals at doses that were not toxic to the mother, indicating that the young are more sensitive to lindane than the adult animal. The risk assessment is conducted to ensure that the level of human exposure is well below the lowest dose at which these effects occurred in animal tests. Only uses for which exposure is well below levels that cause no effects in animal testing would be considered acceptable for registration.

Residues in Water and Food

This analysis is an estimate of the dietary burden to humans resulting from past seed treatment use of lindane in Canada. It does not account for existing amounts in human body tissues.

Dietary risk affects two distinct populations in Canada: the general population and the Northern, aboriginal peoples. The general population would be exposed to lindane residues from treated crops and livestock that constitute market foods, and from drinking water. The Northern communities, however, would be exposed to lindane through market food and traditional food (hunting and fishing), with little exposure from drinking water.

In the general population, chronic and cancer exposure estimates are unacceptable from both drinking water and food consumption. In addition, the children of the general population are subject to acute risk from drinking water. Northern communities also have unacceptable cancer risk from their consumption of market food.

The dietary risk estimates could be refined with livestock feeding studies, along with better estimates of drinking water concentrations. However, both occupational and environmental risks are presently unacceptable and seem unlikely to be mitigated. A review of additional dietary data would not result in an overall conclusion of acceptability.

Occupational Risks From Handling Lindane

The occupational risk assessments considered exposures to workers treating seed in commercial facilities and on-farm as well as to workers handling and planting treated seed. Exposure scenarios were highly refined using chemical-specific and use-specific information. Maximum personal protective equipment, by way of protection factors for dermal and inhalation mitigation, were also applied to the risk assessment where appropriate. Further mitigation measures such as the use of polymeric coatings on treated seeds and closed cabs for planting treated seeds were also included in the planting assessment.

Even with these refinements and mitigation, risk to workers treating or planting treated seed is unacceptable.

Environmental Considerations

What Happens When Lindane Is Introduced Into the Environment?

Lindane accumulates in the environment

When lindane is applied as a seed treatment to control insect pests in crops, a large quantity of it finds its way into soil, air and water after the seeds are planted. The chemical is expected to persist in soil and water as it is not broken down rapidly by soil microbes or by chemical reaction in water. Lindane has low mobility in soil; however, field studies have shown that lindane can contaminate groundwater. Water runoff on the soil surface can move residues into nearby bodies of water, for example, ponds and rivers. Lindane is released readily as a gas via the soil from crops such as canola and cereal seed. It enters the atmosphere in large amounts compared to the amount that is applied to seeds. By taking the total acreage of treated canola in a given year, an estimate of 28 to 191 tonnes of lindane would be released from the Canadian Prairies annually.

Once in the air, lindane is persistent and moves through the atmosphere to regions that are far removed from its area of use. Lindane moves from the Canadian Prairies to the Great Lakes region and the Canadian Arctic, where it is deposited through the process of condensation. As a result, lindane is detected not only in the air, but also in precipitation, oceans and rivers, in wildlife such as birds, fish, whales, seals, wolves and caribou and in humans. Concentrations of lindane in lakes and rivers are higher in western Canada than in eastern Canada, explained by the use of lindane on canola in the Prairies.

Lindane accumulates in wildlife to levels that are cause for concern. Not only does lindane bioconcentrate and bioaccumulate to high levels, particularly in fish, but it also biomagnifies in some animals such as lake trout, seals and whales.

Lindane was never manufactured in Canada. In other countries, its manufacture produced large quantities of waste chemicals that have similar chemical properties to lindane. Improper storage and disposition of this waste allows for its release into the atmosphere and global waters and entry into the Canadian environment.

For every tonne of lindane produced, six to nine tonnes of waste chemicals must be disposed of or otherwise managed. One management option reported by industry is to transform the waste isomers into trichlorobenzene and hydrochloric acid. However, the PMRA can neither confirm nor ensure this process is being used to manufacture lindane outside of Canada. The use of lindane in Canada could contribute to the production of these waste chemicals. As with lindane, these waste chemicals are persistent and are found not only in the air, but also in precipitation, oceans and rivers, wildlife such as birds, fish, whales, seals, wolves and caribou, and in humans. Given the toxicity and environmental levels of the waste chemicals and their potential for long-range transport, the PMRA remains concerned that the production of lindane overseas would result in further contamination of the Canadian Arctic.

Lindane is considered as arising from anthropogenic sources and is also considered to be "CEPA-toxic Equivalent" under the Canadian Environmental Protection Act because it is entering the environment at levels that pose a risk to terrestrial and aquatic organisms. Lindane also meets the Government of Canada's Toxic Substances Management Policy (TSMP) Track 1 criteria for persistence in the environment. Lindane does not technically meet the TSMP Track 1 substance criteria for bioaccumulation. However, based on the strong evidence for biomagnification, particularly in organisms at the top of the food webs, the PMRA has serious concerns about the contamination of food webs.

The α- and β-isomers of hexachlorocyclohexane are waste chemicals that result from the manufacture of lindane. Both meet the TSMP Track 1 criteria for persistence in the environment. Bioaccumulation of the β-isomer in fish meets the TSMP Track 1 criteria for bioaccumulation.

Lindane poses a potential risk to terrestrial and aquatic organisms

Terrestrial organisms such as birds and small mammals are at risk from feeding on lindane-treated seeds in agricultural fields (for example, in fields planted with canola seed). Birds and small mammals can be killed after consuming a small number of lindane-treated seeds, especially canola seed. Lindane also has the potential to affect reproduction in birds and small mammals. Soil invertebrates such as earthworms are also potentially at risk.

For aquatic organisms, water monitoring and model estimations of concentrations in bodies of water (rivers and wetlands) have revealed lindane concentrations above the level of concern. In freshwater fish, lindane can pose an acute risk in some species. For marine invertebrates in shallow estuarine/marine habitats, lindane poses an acute risk and possible fertility problems.

Measures to Minimize Risk

Risk-reduction measures to address some of the potential risks from lindane use are identified in Re-evaluation Note REV2009-08, Lindane Risk Assessment, but are not proposed for implementation. It is not feasible to reduce risks sufficiently to address the levels of concern that have been identified for the following.

Human Health

Even with maximum personal protective equipment and engineering controls, risks to workers handling lindane and lindane-treated seed are unacceptable.

Environment

As a seed treatment, there are no effective measures from an environmental perspective to mitigate the volatilization, atmospheric transport, bioaccumulation and toxicity of lindane.