Coal Tar & PAHs in the Real Environment

Transcription

1 Coal Tar & PAHs in the Real Environment The time for using the Precautionary Principle in regulation of PAH-containing materials is past International Tar Association Prague, Czech Republic September 2017

2 2 State of Knowledge about Coal Tars (& Distillates) & PAHs in the Environment Recap At Seoul meeting, reviewed current stateof-the-science re occupational exposures to PAH-containing substances Conclusion: Hazard classifications of CT, CTP, PAH-containing materials should be reconsidered 1 st Draft of ITA-funded manuscript is nearly complete

3 3 State of Knowledge: CT/PAHs in the Real Environment Today: CT & PAHs in the Real World Sources of PAHs in the Environment Human Health Impacts Ecological Impacts

4 State 4 of Knowledge & Regulation Paper in review by Dr. A. Moghissi (Inst. Reg. Sci. & Georgetown University) PP as basis for regulation may be appropriate when uncertainty is high As knowledge increases, uncertainty decreases & regulation based on knowledge is appropriate

5 5 Knowledge of PAHs & CT in Real World 1970s through 1990s Regulatory basis for PAHs & CT established Based on Precautionary Principle Largely based on a few laboratory studies of individual PAH compounds AND perception that PAHs were bad actors in uncontrolled emissions during early industrialization Coal Tar Little & PAHs in the Real Environment data on CT in the environment

6 6 What is the State of Knowledge about CT & PAHs in the Real Environment Today? PART 1 Sources of PAHs in the Environment

7 7 Sources of PAHs in the Environment Can sometimes identify broad categories of sources based on distribution of individual PAH compounds ( fingerprint ) Petrogenic (fossil fuel: crude oil, coal) Pyrogenic (combustion sources, including CT, vehicle exhaust, wood fires) Biogenic (natural biologic processes)

8 8 Inventory of PAHs Commonly Used in Fingerprinting Studies Stout et al., 2004

9 9 Distribution of Individual PAHs (& congeners) Boehm et al., 2002

10 10 PAHs from CT & Other Sources Dominated by Parent PAH; Alkylated PAHs Prevalent in Lower Temperature Processes This sample was Coal Tar Boehm et al., 2002

11 11 Petrogenic vs. Pyrogenic vs. Biogenic Can be easy to distinguish broad categories using methods involving analysis of distribution of individual PAHs. Distinguishing among pyrogenic sources (which includes CT) is not so easy

12 12 PAH pattern distribution works best for identifying known LOCAL sources, but WEATHERING

13 13 Weathering: PAHs from pyrogenic sources weather to similar-looking patterns Stout & Gaan, 2010

14 14 Difficult to Parse Pyrogenic Sources The similarity in the assemblage of PAHs produced by different combustion processes makes the apportionment of sources a difficult task. In addition, burning conditions can significantly influence the relative proportion of PAHs from a single source, adding to the complexity of estimating the relative contributions of the major sources of pyrogenic PAHs. Lima et al., 2005

15 Analytical 15 Method is Key Many papers in the science literature use an inadequate analytical method, but hey! it s a publication, so what could go wrong? This is another of many problems with USGS papers on CT-based sealants

16 16 A Completely Different Approach: Mass Balance Add up estimated emissions from all known sources Labor intensive, therefore expensive New York New Jersey Harbor Study

17 17 Mass Balance Puget Sound (Seattle) Study

18 18 Comprehensive local study: Impact of Sydney (Nova Scotia) Tar Pond on area soils & sediment (Spoiler Alert not much) Results indicate coal combustion (from historical residential, commercial and industrial uses) and coal handling (from historic on-site stockpiling and current coal transfer and shipment facilities) are likely the principal source of PAHs found in urban soils and marine sediments, consistent with current and historical activities near these sites. However, PAH fingerprints associated with STP sediments correlated poorly with those of urban soils and marine sediments, but were similar to coal tar, historically consistent with by-products produced by the former coking operations. This study suggests PAH contamination of Sydney Harbour sediments and urban soils is largely unrelated to historic coking operations or recent remediation of the STPs site, but rather a legacy of extensive use of coal for a variety of activities. (MacAskill et al., 2016)

19 19 Pearson Correlation Coefficients (r) Sydney (NS) Tar Pond & other nearby sediments

20 20 State of Knowledge about Real World Sources of PAHs Most significant source of PAHs in the environment in the US is related to wood burning Second sources are vehicle emissions Power generation (recent CF plants in US)single-digit percentage Over regulation of small sources, waste of government & industry resources

21 21 What is the State of Knowledge about CT & PAHs in the Real Environment Today? PART 2 Human Health Impacts

22 22 Occupational Exposure Studies Summary from 2016 Presentation (more or less) 5 recent systematic reviews & meta-analyses of published occupational exposure in workplaces where PAHcontaining materials are used Most relative risk values <2 (all less than 3; many indistinguishable from 1) Facilities using Södeberg process may have greatest relative risk Although any measure of risk would follow a continuous distribution and there are no predefined values that separate strong from moderate or weak associations, relative risks below 3 are considered moderate or weak. (Boffetta2010)

23 23 Canada: 2016 Draft Screening Assessments Margin of Exposure Approach Formally used by UN WHO Joint Expert Committee on Food Additives (JECFA) European Food Safety Agency (EFSA) Values > 10,000 = no/low concern Low priority for risk management

24 24 Canada: 2016 Draft Screening Assessments (2) Risk from the processing, handling and storage of coal tars and their distillates at a coal tar refinery Benzene inhalation MOE = 10,140 12,890 B(a)P MOE = 195,000 Risk from the production, handling and storage of coal tar at integrated steel mills Benzene inhalation MOE = 13, ,640 B(a)P MOE = 255,000 Risk from the transport of coal tars and their distillates The transportation of coal tars and their distillates is not considered to be a risk to human health.

25 25 Canada: 2016 Draft Screening Assessments (3) Risk from PAHs in house dust associated with use of coal tar-based pavement sealants Lifetime adjusted PAH MOE = 15,500 PCTC commissioned a review by a subject area expert, who identified 4 choices Canada made that increased the conservatism of an already conservative method. Re-calculation changing just 2 of the additional layers of conservatism resulted in MOE = 105,000 Risk from inhalation exposure to coal tar-based pavement sealant application short-term health effects are limited, localized and generally reversible Risk from dermal exposure resulting from coal tar-based pavement sealants Given the infrequent nature of the exposure and the limited duration for which it is expected to occur, the conclusion is that incidental dermal exposure to CTPS does not constitute a human health concern.

26 26 US: 2017 Release of Revised B(a)P IRIS Assessment Good: Revised cancer potency (dose) values Lowered oral (diet) potency by a factor of 7 (7.3 mg/kg day to 1 mg/kg/day) Problematic data resulted in EPA removal of draft dermal assessment Modified inhalation values to acknowledge impact of particle loading Not so good: Hazard assessment remains problematic Why is this important? B(a)P used as the index compound by USEPA and others in a relative potency method of adding up potential risks using individual PAH concentrations.

27 Estimated 27 human doses of carcinogenic PAHs from food, air, water, soil although cereal groups might not have the highest concentration of carcinogenic PAHs, they are a major component by weight of the total diet.

28 28 Recent studies confirm that PAH bioavailability & absorption varies with source of PAHs CT/CTP is least readily absorbed Xia et al., 2016

29 29 Bioavailability & Absorption Studies CT Pitch (skeet) - Slowly absorbing cpahs - Result Very low PAH absorbed (in bloodstream) - Higher percentage of irreversibly bound cpahs than any other matrix studied Ruby et al., 2016

30 30 State of Knowledge about Real World CT/CTP & PAH Human Health Impacts Indicate that regulation based in laboratory studies of individual PAH compounds is significantly over-cautious Result is unwarranted (over)regulation Waste of government & industry resources

31 31 What is the State of Knowledge about CT & PAHs in the Real Environment Today? PART 3 Ecological Impacts

32 32 Adverse ecological impacts: Difficult to find examples of association with PAHs In 2017, PCTC commissioned a review of relevant literature by a well known aquatic toxicologist Result In assessing potential risk of runoff/release of coal tar sealant products to aquatic organisms, it is important to distinguish between the following questions: Can coal tar sealant products cause adverse effects in laboratory tests? Does coal tar sealant products cause adverse effects in the field? My review of the scientific literature indicates that the weight of evidence is not sufficient to conclude that refined coal tar sealants are causing adverse effects to aquatic organisms in the environment.

33 33 Toxicity of PAH-Containing Sediments (Neuhauser et al. 2006) 9

34 34 PAH concentrations in the Anacostia River (Wash., DC) sediments not correlated with toxicity

35 35 Predicted vs Actual PAH Toxicity (Anderson et al. 2011) 10

36 36 State of Knowledge about Real World CT/CTP & PAH Ecological Impacts Difficult to find examples of adverse ecological impacts related to PAHs Indicate that regulation based in laboratory studies of individual PAH compounds & of PAH-containing materials is significantly overcautious. Result is unwarranted (over)regulation Waste of government & industry resources

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40 40 Questions? Anne LeHuray, Ph.D Mount Vernon Ave., Ste. 134 Alexandria, VA (703)