The Canadian government recently called for closer scrutiny of a chemical called “quinoline” entering the environment. To my knowledge there is no similar requirement in the US. What is it and why are they monitoring it? Is it a problem with coal tar sealants?
As you will recall, PAHs are a family of chemicals with multiple benzene rings (all carbon on the inside of the rings), but quinoline is like that except there is a nitrogen in place of a carbon as shown in the picture below.
I first became acquainted with quinoline when looking at methods to differentiate coal tar sealants from asphalt sealants. In a 1999 paper, Koppers Industries, the largest supplier of refined coal tar in the US, discussed various methods of testing the quality of tar substitutes and one of those was the “quinoline insolubles” or QI. It is a measure of the remaining portion of a solid in a quinoline solution. The portion of a coal tar that does not dissolve in quinoline is considered the QI. The “coffee/tea test” or field test for coal tar sealants is based upon this understanding, but with a common hardware solvent, paint thinner. More details about the field test can be found here.
So why look at this chemical? Unlike PAH’s, quinoline is highly water soluble and toxic to aquatic life in solution. It may be part of the problem with washoff of freshly sealed coal tar sealants. A 1 inch rain on top of a freshly sealed coal-tar application creates a toxic brew about 7,000 times higher than the effects concentration on fish!
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| Quinoline molecule |
Quinoline concentrations in wet sealcoat were in the order of 1000 mg kg-1 or 0.1 % w/w. This concentration decreased to, on average, 170 mg kg-1 in the dried commercial emulsions, 51 mg kg-1 in CTS samples, and 50, 34 and 11 in asphalt sealcoat, uncoated asphalt and ‘other’(Figure 11). The volatility of quinoline allowed for an 80-90 % loss of mass during the 48-hour drying process of the commercial sealcoat samples and a further 30 % loss relative to CTS samples.
Final_report_cts Aug 9 (1)
A summary of Environment Canada’s findings:
Based on the information presented in this draft screening assessment, it is proposed that quinoline is entering or may be 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. 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 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.
It is therefore proposed that quinoline meets the criteria 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 (Canada 2000).
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.