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Shannon Murphy, Ph.D.
Office of Environmental Health Hazard Assessment California Environmental Protection Agency
Delta Tributaries Mercury Council
September 13, 2016
OEHHA mandate
Chemicals of concern and health risks
Health benefits of eating fish
Advisory development process
Recent OEHHA advisories
Hg, PCBs
OEHHA Fish Advisory Program
California Health and Safety Code
Section 59009, to protect public health
Section 59011, to advise local health authorities
California Water Code
Section 13177.5, to issue health advisories
www.oehha.ca.gov/fish/advisories
Chemicals of Concern and Health Risks
Hg, PCBs
Pictures from California Geological Survey and USGS
Mining, fossil fuels, volcanoes Industrial lubricants
Legacy pesticides
Discharges into sewer systems and waterways
Flame retardants
Why is Mercury in Fish a Concern?
Fish consumption is the major source of mercury exposure for most people
Almost all fish contain some mercury
Hg, PCBs
Mercury can change forms:
Mercury can be methylated to form MeHg in certain aquatic environments
Methylmercury (MeHg)* is the more toxic and most common form of mercury found in fish
Hg+CH3 (mercury + methyl)
*MeHg and mercury will be used interchangeably in this presentation
Hg, PCBs
Are mercury levels different in different fish species?
Predator fish have more mercury than prey fish; Older fish have more mercury than younger fish
Hg, PCBs
…The brain is target organ of methylmercury toxicity
Adults with high exposures reported:
• Mental confusion • Loss of balance • Irritability • Fine tremors • Numbness and tingling • Changes in vision
Hg, PCBs
…The fetus is more sensitive to the effects of methylmercury than adults
Passes through the placenta to
the baby
MeHg = methylmercury
Hg, PCBs
…Children are also more sensitive than adults
The developing nervous system is more sensitive to toxins, including methylmercury, than adults
Effects occur at lower exposures in the fetus and children than in adults
Hg, PCBs
How do we determine a safe level of mercury exposure?
Several large studies conducted on children in seaf00d-eating populations
Faroe Islands, Seychelles Islands, New Zealand
Identify lowest dose with an adverse effect
Hg, PCBs
How is this information used to set safe exposure levels?
USEPA sets something called an oral reference dose (RfD):
An estimate of a how much of a chemical people can be exposed to every day over their entire lives without significant risk of getting sick as a result Includes sensitive individuals
Incorporates uncertainty factors to account for incomplete data and individual variability (for MeHg, UF = 10)
Hg, PCBs
MeHg Reference Dose (RfD)
The newer RfD was set to protect the fetus and young children
The original RfD was based on effects in adults and is 3 times higher (i.e., adults are 3 times less sensitive)
Hg, PCBs
OEHHA uses the RfD:
To recommend the maximum number of fish servings to eat each week at a location
OEHHA uses the MeHg RfD to make fish consumption recommendations for women 18-45 years and children 1-17 years
OEHHA uses the original RfD to make fish consumption recommendations for women 46 years and older and men 18 years and older
Hg, PCBs
Why are PCBs and Pesticides in Fish a Concern?
PCBs and legacy pesticides (chlordanes, DDTs, dieldrin, toxaphene) do not break down easily
Bioaccumulate in fish
May effect nervous system development in fetuses or children
Some of these chemicals have caused cancer in animals
Emerging concern: PBDEs can be developmental and reproductive toxicants
Hg, PCBs
Can warning people about contaminants in fish have unintended negative consequences?
2007 National Report: “Seafood Choices: Balancing Benefits and Risks”
State fish advisory “warnings can change perceptions and beliefs….
….but unintended effects, such as overreactions, may occur”
Hg, PCBs
What are “Omega-3s”
A specific type of polyunsaturated fat
ALA – shorter compound
DHA and EPA – longer compound
Research has shown “omega-3s” to have beneficial effects on the heart
Major Dietary Omega-3s
ALA (Plant-based)
Flaxseed Oil
Walnuts
Canola
DHA
Fish oil
Breast milk
EPA
Fish oil
Beneficial effects on the heart:
Lower risk of abnormal heart beats
Lower triglyceride levels
Slowed growth of plaque in the arteries
Slightly lower blood pressure
What about the benefits of fish consumption during pregnancy?
Benefits the developing nervous system in the fetus
Not yet well understood whether the benefits of fish consumption during pregnancy are:
solely the result of omega-3s in fish or
due to some combination of nutrients that may include omega-3s
FDA/USEPA, 2014
Fish you can catch in California that have higher omega-3 levels
Salmon
Rainbow trout
Brown trout*
Steelhead
Shad
Bass* – largemouth, smallmouth, striped
*May contain high levels of MeHg – check statewide or local advisories
Historic Gold and
Mercury Mines
in California
Source for Gold and Mercury Mines data: U.S. Geological Survey (USGS). 1998. Minerals Availability System (MAS/MILS database). By J. Douglas Causey. USGS, Denver, CO.
Altoona Mine
OEHHA’s Approach to Advisories
OEHHA, 2008 and 2011
Data Evaluation
Evaluate and select available fish contaminant data from a water body.
Ensure that data meets quality criteria and sampling plan guidelines.
Select Species
Determine fish species for which adequate data are available to issue advice.
Calculations
Calculate appropriate measure of central tendency (often weighted mean), and descriptive stats of contaminant data for chemicals of potential concern for selected species.
OEHHA’s Approach to Advisories (continued)
OEHHA, 2008 and 2011
Advisory Tissue Levels (ATLs)
Compare chemical concentrations with ATLs for each chemical of potential concern; evaluate Hazard Indexes for potential exposure to multiple chemicals for the sensitive population.
Develop Advice
Develop advice based on thorough data review and best professional judgement; consider local/cultural practices and regulations (legal fish size or take), local fishing pressure, geography/access and environmental justice factors.
Advisory Tissue Levels (ATLs)
ATLs- acceptable chemical levels in fish tissue, based on chemical toxicity across a range of consumption rates
Not “bright lines”
Part of a complex process of data evaluation and interpretation
Builds on Fish Contaminant Goals (FCGs-do not consider benefits)
Incorporates benefits and risks
Considers the sensitive population (MeHg)
OEHHA, 2008 and 2011
Data Sources
CEDEN: California Environmental Data Exchange
Network
USGS studies
UC Davis studies
SWRCB and Regional Board efforts
FERC: Federal Energy Regulatory Commission
Licensing bioaccumulation studies
Sampling Plan Criteria (Minimum)
3 target species
9 individuals/species (legal/edible size)
3+ collection sites, depending on water body size
Seasonal - avoid collection during spawning
Collect during typical fishing season for target species
OEHHA, 2005
Data Criteria (Minimum)
Appropriate sample handling and processing
chain of custody
Skinless fillets or eviscerated whole bodies (prey fish)
QA/QC verification and appropriate methods used
Report moisture and lipid concentrations
Results expressed as wet weight (preferred)
OEHHA, 2005
New Fish Advisories 2015-2016 Water Body Chemical Driver Species
Lake Piru (Ventura County)
Mercury Black Bass, Brown Bullhead, Sunfish
Shadow Cliffs Lake (Alameda County)
Mercury, PCBs Black Bass, Carp, Catfish, Sunfish
Lexington Reservoir (Santa Clara County)
Mercury
Black Bass, Inland Silverside, Rainbow Trout, Sunfish, Threadfin Shad
French Meadows Reservoir
(Placer County)
Mercury
Brown Trout, Rainbow Trout, Crayfish
Hell Hole Reservoir (Placer County)
Mercury
Brown Trout, Crayfish, Kokanee, Lake Trout
Elkhorn Slough (Monterey County)
Mercury, PCBs
Asian Clam (Corbicula), Bat Ray, Leopard Shark, Speckled Sanddab,
Surfperch
OEHHA Collaborators
SWRCB and Regional Boards CDPH
SWAMP CDFW
BOG UC Davis
Delta MERP DTMC
Visit us at www.oehha.ca.gov/fish