Mercury: What’s going on?

1. Mercury: What’s going on? Michelle Woolfolk, Modeling Unit Discharger meetings: December 18, 2002 and January 15, 2003

2. Questions • Why is mercury a concern? • How much mercury is acceptable in surface water? Fish? • Is there any evidence that mercury is a problem in North Carolina? • Why is the coastal area a target (versus mountain or piedmont)? • What is the source of mercury in surface water? Fish?

4. NC Fish Eating Advice • Issued in April 2002 • Advises restricted consumption of largemouth bass, chain pickerel, bowfin caught from NC waters • Establishes range of south and east of I-85

5. Confusing Issue #1: How high is too high? (Criteria) • Federal criteria • Food and Drug Administration (FDA): 1 mg/kg • Environmental Protection Agency (EPA): 0.3 mg/kg • After careful review and consideration by the NC Air Quality Scientific Advisory Board, • NC Dept of Health and Human Services: 0.4 mg/kg

6. Water Quality Criterion: Methylmercury • EPA published January 2001 • Tissue Residue Criterion of 0.3 mg/kg • Calculated using human health risk assessment methodology • Target water concentration back-calculated using multiple site-specific factors • water to fish bioaccumulation factor • total mercury to methyl mercury translator

7. Risk from Methylmercury Exposure • Adult nervous system effects at high levels • Nervous system of developing fetus affected at lower exposure levels • Recent Studies • Seychelles, Faroes Islands, New Zealand • Varying estimates of “no risk exposure” • SAB: 0.17 mg/kg/day Presented to EMC by G. Lucier, PhD of the SAB

8. Environmental Exposures to Methylmercury • Mercury is ecologically and biologically persistent • Exposures measured through fish consumption and methylmercury levels • Hair: effective measures of past exposure Presented to EMC by G. Lucier, PhD of the SAB

9. North Carolina Hair Mercury Levels* *Provided by Dr. Gregory Smith, NC DHHS Presented to EMC by G. Lucier, PhD of the SAB

10. Confusing Issue #2: How to define areas of concern ? • Criteria, apply as mean, median, or reasonable maximum • Fish tissue data • Easily recognizable by the general public

12. 5/11/2001

13. 4/24/2001

14. Confusing Issue #3: What is DWQ doing in all this mess ? • Fish consumption advisories indicate a loss of use of a water body, so • Waterbodies are impaired (303(d) list)!!! • DWQ administers the NPDES program • DWQ and EPA are responsible for developing Total Maximum Daily Loads for these waterbodies

15. Confusing Issue #4: Where is the mercury coming from ? • Direct discharges of wastes containing mercury • Indirect discharges of mercury from • Air (wet and dry deposition) • Overland runoff (residential and industrial areas, and wetlands)

16. But, it’s even more confusing than that • Mercury from air can be from local sources or from across the globe • Just because mercury gets into the aquatic system doesn’t mean it will accumulate in fish • AND everything depends upon the form of mercury (Hg0, Hg2+, MeHg)

17. Predicting the Impact of Airborne Mercury Emissions Hg can travel long distances before depositing Hg emitted to air or overland runoff End consumer Hg accumulation in fish Hg in water transforms to MeHg Presented to EMC by G. Lucier, PhD of the SAB

18. Wetlands… Good for the environment!(Except for mercury) More MeHg Out MeHg In • Wetlands export much more MeHg than they receive Presented to SAB by R. Harris, PhD of the TetraTech, Inc.

19. What kinds of lakes tend to have higher fish Hg? • Low productivity • Low pH • Moderate to high DOC • Presence of wetlands • Smaller, warm lakes Presented to SAB by R. Harris, PhD of the TetraTech, Inc.

20. Mercury Deposition Network (MDN) • Weekly collections • Hg concentration, precipitation, deposition

21. Total mercury in aquatic environments Sources: USGS 2000 and MCFRBA

22. Because we can’t tell how much mercury is in water or effluent!!! Why should DWQ use Method 1631?

24. Methyl mercury in aquatic environments Source: USGS 2000

25. Mercury Cycling in D-MCM Wet and dry Deposition Volatilization Outflow Hg(0) Inflow/Runoff Reduction Photodegradation Oxidation Hg(II) MeHg Settling/Resusp Diffusion Settling/Resusp Diffusion Bioaccumulation Hg(II) MeHg Burial Burial Demethylation Methylation

26. NC Eastern Regional Mercury Study • Funded by USEPA grant • Goals • Evaluate levels of ambient mercury in surface water systems • Estimate site-specific total mercury:methyl mercury translators to evaluate water quality criteria • Estimate site-specific water to fish bioaccumulation factors • Evaluate potential mercury loads from WWTPs

27. NC Eastern Regional Mercury Study • Using clean methods (handling and analysis, incl. Method 1631) • Study conducted for one year • Monitor quarterly • total and methyl mercury in surface water • total and methyl mercury in sediment • Monitor annually • mercury in fish

28. South and Black Rivers (CPF) Waccamaw River and Lake Waccamaw (LBR) Lumber River (LBR) Eno River (NEU) Contentnea Creek (NEU) Kendricks Creek (PAS) Phelps Lake (PAS) Cashie River (ROA) Ledbetter Lake (YAD) Abbotts Creek (YAD) NC Eastern Regional Mercury Study

29. For more information • DHHS Fish Eating Advicehttp://www.schs.state.nc.us/epi/fish/mercuryadvice.html • SAB mercury review http://daq.state.nc.us/toxics/risk/sab/finalHgReport.pdf • DWQ mercury fish tissue results are reported in basin assessment documents. • EPA Water Quality Criteria http://www.epa.gov/ost/criteria/methylmercury/ • FDA Mercury Advisory http://www.cfsan.fda.gov/~dms/admehg.html • Impaired Waters (Integrated Report/303(d) List) http://h2o.enr.state.nc.us/tmdl/General_303d.htm