#15: Chemicals: Scientific Models #15: Chemicals: Scientific Models ESD.936 Noelle Selin

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1 #15: Chemicals: Scientific Models ESD.936 Noelle Selin

2 Questions/Outline How can models be used to assess chemicals for regulation, particularly internationally? What are the challenges and limitations of screening and assessment tools? Can better models be designed?

3 Availability of Data on 2465 High Production Volume Chemicals; some illustrative properties and toxicities (IUCLID Database, 1999) Chronic toxicity to fish Persistence/Stability in Soil Prop perties and Toxicities Toxicity to Reproduction Bioaccumulation Developmental toxicity/teratogenicity Persistence/Stability in Water Carcinogenicity Acute/prolonged toxicity to fish Acute oral toxicity Data Availability (%) Source: Allanou, R., Hansen, B.G., and van der Bilt, Y. Public Availability of Data on EU High Production Volume Chemicals. European Commission, Joint Research Centre, European Chemicals Bureau: Ispra, Italy.

4 Many Chemicals, Few Risk Assessments 100,000 Chemicals on EU market 75,000 Chemicals with little or no toxicity data 25,000 Chemicals with limited toxicity data 10,000 EU priorities for risk assessment c.2500 High production volume chemicals (HPVC) 42 EU risk assessment priorities Risk assessments finalized, Risk assessments publicly available, 2000 Image by MIT OpenCourseWare.

5 POPs: Specific category of particularly hazardous chemicals Persistent organic pollutants Characteristics: persistence in environment (air, soil, water); bioaccumulate (fish, marine mammals); toxic Category of POPs is a science-policy hybrid Subject to international agreements (global Stockholm Convention)

6 What are POPs and why are they a problem? Pesticides, e.g. DDT, Chlordane: carcinogenic, ecotoxic Subject to international regulation because of long-range transport Accumulation in the Arctic, in Accumulation in the Arctic, in traditional foods, far from location of use/release

7 POPs are a science-policy hybrid POPs chemicals (e.g. DDT, PCBs) have been regulated for decades, but the term POPs emerged as part of science-policy discussions on regulations Number of Papers on "Persistent Organic Pollutant(s)" (ISI Citation Index) Earlier terms included: CLRTAP POPs Protocol signed 150 persistent organic 100 contaminants, persistent 57 organic compounds, POC, persistent semivolatile bioaccumulating organic compounds Regulatory criteria for selecting ect POPs for regulation include: Persistence Potential for long-range environmental transport Bio-accumulation Adverse effects Number of Articles Stockholm Convention signed * Year

8 How to determine whether a chemical is a POP? Data requirements for persistence, bioaccumulation Environmental fate properties and/or Environmental fate properties and/or model results that demonstrate that the chemical has a potential for longrange environmental transport [Stockholm Convention]

9 INTERNATIONAL CRITERIA FOR POPs Bioaccumulation: Bio-accumulation factor (aquatic) > 5000 or log Kow > 5, OR Evid idence of high h bioaccumulation in other species, hi high (eco)toxicity, t OR Monitoring data in biota Persistence: Half-life of 2 months in water, or 6 months in soil, or 6 months in sediment, OR Evidence of sufficient i persistence to justify considerati tion Long-range transport potential: Measured levels in locations far from releases, OR Monitoring showing long-range environmental transport may have occurred, OR Environmental fate properties or model results showing potential ti for transport t Air half-life > 2 days for chemicals transporting through air Adverse effects Criterion Bioaccumulation Persistence Transport Log Kow Bioaccumulation Factor Water Stockholm CLRTAP months 2 months Soil 6 months 6 months Sediment 6 months 6 months Air 2d days 2d days Log Kow=octanol-water partition coefficient, measure of lipophilicity Bioaccumulation factor: takes into account environmental and dietary sources] [Eckley, Environment, 2001; Rodan et al., ES&T,

10 SETTING CRITERIA: WHERE ARE THE DIRTY DOZEN? T Graph removed due to copyright restrictions. Please see Figure 2 from Screening for Persistent Organic Pollutants: Techniques To Provide a Scientific Basis for POPs Criteria in International Negotiations, by Rodan, et al. Published in Environmental Science & Technology, vol. 33, no. 20, (1999). [Rodan et al., ES&T, 1998]

11 POPs Included and Proposed under Major Agreements l chemica als Bypr roducts Pest ticides Industria Stockholm Aldrin Chlordane Chlordecone P DDT Dieldrin Dioxins Endosulfan Endrin Furans Heptachlor Hexabromobiphenyl P Hexachlorobenzene Hexachlorobutadiene P Hexachlorocyclohexane P Mirex Octabromodiphenyl ether P P PCB Pentabromodiphenyl ether P P Pentachlorobenzene P P Perfluorooctanesulfonate P P Polychlorinated naphthalene P Polycyclic aromatic hydrocarbons Short-chain chlorinated paraffins P P Toxaphene Chemical CLRTAP Proposed- CLRTAP Proposed- Stockholm [Selin and Selin, Review of European Community and International Environmental Law, 2008] P

12 SCREENING FOR ADDITIONAL POPs Transport Distance v. Model Overall Environmental Persistence Other approaches to identify POPs: Graph removed due to copyright restrictions. Please see Figure 4 from Screening for Persistent Organic Pollutants: Techniques To Provide a Scientific Basis for POPs Criteria in International Negotiations, by Rodan, et al. Published in Environmental Science & Technology, vol. 33, no. 20, (1999). Model overall environmental persistence (sometimes, different results from half-life approach, see Klasmeier et al. 2006) Screening based on quantitative structureproperty relationships (Muir and Howard, [Rodan et al., ES&T, 1998] 2006 identified 30 with bioconcentration potential and 28 with transport potential) But, challenges in monitoring and measurement exist.

13 ADDITIONAL CONSIDERATIONS AND CHALLENGES Known, regulated POPs (e.g. PCBs, dirty dozen pesticides) have data available, but many of the intentionally-produced ones are no longer produced Byproduct POPs (dioxins, furans) regulated in industrialized countries, continue to grow elsewhere Candidate POPs (e.g. PFOS, PBDEs) have some data, and are emerging problems. Unidentified POPs --???

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