Synopsis

Under the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment of quinoline, Chemical Abstracts Service Registry Number 91-22-5, which was a substance on the Domestic Substances List (DSL) selected for a pilot project for screening assessments.

Quinoline is naturally associated with coal and coal-derived compounds and may be formed as a trace pollutant during incomplete combustion of nitrogen-containing substances. Potential sources of quinoline releases to water and air include discharges of creosote, coal tar and associated contaminated groundwater from coal tar distillate (creosote) facilities, wood impregnation plants, abandoned coal gasification plants (or gasworks, of which there were approximately 150 in Canada in 1987), steel plants equipped with coke ovens, aluminum smelters and waste incinerators. Many of these releases are a result of past industrial activities. It should be noted that environmental protection measures have been implemented in Canada , in particular for steel plants equipped with coke ovens and for wood preservation facilities. In the case of abandoned gasworks, many sites have been the object of restoration plans due to provincial and federal legislation. Although these initiatives have targeted pollutants such as polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene and xylenes, they should also be effective in addressing quinoline contamination. In addition, creosote-impregnated waste materials from creosote-contaminated sites, PAHs and benzene have been placed on Schedule 1 of CEPA 1999.

Quinoline has been measured in the atmosphere of urban areas. Due to known releases of PAH, air emissions of quinoline are also likely associated with steel plants equipped with coke ovens and aluminum smelters. Vehicle emissions may also contribute to the release of quinoline to air, although the proportion of releases that can be attributed to this source is unknown. Atmospheric releases reported to the National Pollutant Release Inventory in 2008 totalled 445 kg, and 58 tonnes were incinerated off-site. No release to water was reported. Releases to the NPRI were reported by chemical manufacturers, an iron foundry and a waste treatment and disposal facility.

Based on a survey conducted under section 71 of CEPA 1999, one or more companies in Canada reported manufacture or import of quinoline in excess of 20 000 kg during the calendar year 2000 as part of mixtures of which quinoline is less than 1% of the composition.

Quinoline has been detected in coal tar-based products, such as sealcoats used on parking lots and driveways and creosote used in the past as a preservative in the lumber and wood industries, in Canadian Marketplace. However, quinoline is not a registered active ingredient or formulant in Canada. Quinoline was also identified as being used as a component in fragrance mixtures.

Although none of the following uses were reported in response to the section 71 notice, literature sources identified a variety of uses for pure quinoline. Quinoline is used as a solvent, chemical intermediate and corrosion inhibitor and in the manufacture of pharmaceuticals. Industrial applications of quinoline include the manufacture of methine dyes and terpene production; quinoline is also used as a decarboxylation reagent, a solvent of PAHs in paint production, and a chemical intermediate and an anti-foaming agent in petrochemical manufacturing.

Quinoline is not persistent in surface waters. This substance has been shown to be biodegradable in soil under conditions favouring the growth of microorganisms. However, field evidence suggests that quinoline is difficult to degrade by deep soil and groundwater microorganisms. In general, these media offer poor conditions for biodegradation, such as low oxygen levels, low temperatures and few carbon sources. An absence of significant degradation of quinoline associated with the occurrence of coal tar in soils has been frequently observed. Quinoline is expected to persist in air in wintertime, by virtue of an atmospheric half-life exceeding 99 hours and a moderate vapour pressure.

Based on Level III fugacity modelling of the substance’s fate in the environment, if released to surface water, quinoline will remain for the most part in that compartment. Similarly, if released to soil, the molecule will remain mainly in soil. If released to the atmosphere, because of its relatively low volatility, 82% of quinoline will partition to soil and surface water, and the remainder will stay in air. According to a model (TaPL3) assessing the long-range transport potential of substances, quinoline is predicted to be transported for long distances (e.g., >1500 km) in water, but not in the atmosphere.

Quinoline has a low potential to bioaccumulate. It has been shown that biotransformation of quinoline in bacteria, fish and laboratory mammals leads to the formation of an active epoxide intermediate. Some epoxide forms can bind to proteins and nucleic acids and potentially lead to genotoxicity. Consistent with this metabolic activation, quinoline has been shown to be genotoxic in both in vivo and in vitro assays.

Although surface water standards for quinoline have been adopted in many provinces, quinoline is not routinely measured in any environmental medium in Canada, and few sampling data were available for this assessment. However, quinoline is a constituent of coal tar and creosote, and any past or present industrial activity that has released coal tar or creosote into the environment has included the release of quinoline. Most often, releases are to the subsurface as a result of leaking storage tanks, and pools of pure coal tar have been discovered at many abandoned gasworks sites, many of which reaching nearby watercourses.

For the ecological portion of this screening assessment, an exposure scenario was designed whereby a contaminated groundwater plume containing quinoline develops from a pure coal tar pool in the soil and eventually comes into contact with surface waters. It was based on field observations of coal tar plumes made at abandoned gasworks sites and coke oven sites in Canada. This exposure scenario would be relevant to abandoned gasworks and coke ovens and current industrial applications producing or handling coal tar or creosote on-site, including coal tar distillation plants, creosoting plants and roofing felt and tarred paper manufacturing facilities. Estimated dissolved quinoline concentrations were many times above the predicted no-effect concentration of 3.4 µg/L calculated for fish. Based on the risk quotients calculated in this assessment, quinoline has the potential to cause harmful effects to groundwater microorganisms, organisms living at the sediment-water interface and early life stages of fish found on spawning grounds.

On the basis of ecological hazard and reported releases of quinoline, it is proposed that this substance is entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity.

A critical effect for the characterization of risk to human health is carcinogenicity, based on the observation of hemangioendotheliomas in multiple strains of rats and mice exposed orally. In addition, quinoline induced hepatoadenomas and carcinomas following intraperitoneal injection and initiated skin tumours following dermal application in mice. Quinoline was also genotoxic and mitogenic in several in vitro and in vivo assays. Therefore, although the mode of induction of tumours has not been fully elucidated, it cannot be precluded that the tumours observed in experimental animals resulted from direct interaction with genetic material.

General population exposure to quinoline is expected mainly through inhalation. Comparison of the critical effect level for non-neoplastic effects (i.e., 25 mg/kg body weight [kg-bw] per day) with the upper-bounding estimate of exposure (i.e., 0.03 µg/kg-bw per day) results in a margin of exposure of approximately 5 orders of magnitude. If exposure to quinoline through the use of consumer products is considered, the margin of exposure still remains within the same order of magnitude. These margins of exposure for non-neoplastic effects are considered adequate.

On the basis of the carcinogenicity of quinoline, for which there may be a probability of harm at any level of exposure, it is proposed that quinoline is a substance that may be entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

Based on available information for environmental and human health considerations, it is proposed that quinoline meets one or more of the criteria set out in section 64 of CEPA 1999.

Additionally, it is proposed that quinoline meets the criteria for persistence but not for bioaccumulation potential as set out in the Persistence and Bioaccumulation Regulations.

This substance will be considered for inclusion in the in the Domestic Substances List inventory update initiative. In addition and where relevant, research and monitoring will support verification of assumptions used during the screening assessment and, where appropriate, the performance of potential control measures identified during the risk management phase.