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Human Health Risk Assessment

Robert Pitt, P.E., Ph.D., DEE

Department of Civil and Environmental Engineering

University of Alabama

Tuscaloosa, AL 35487

Myths of Pollution Control (McKinney and Schoch)

• Myth of Purity in Nature: virtually nothing is “pure” in nature. There are many naturally occurring contaminants, and highly polluted air or water contains only tiny fractions of contaminants (ppm, ppb)

• Myth of Zero Pollution: zero pollution is an unrealistic goal. Modern society produces pollutants and everything must go somewhere.

• Myth of Zero Risk: every activity has risk. Can only minimize, not eliminate, total risks we face. Hindered by inaccurate perceptions of risk.

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Perception of risks strongly determined if observable or controllable (McKinney and Schoch)

Components of Dread (Uncontrollable) and Unknown (Unobservable) Factors (Kammen and Hassenzahl)

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Comparison of Group Rankings (partial list) (Kammen and Hassenzahl)

Eugene, OR, Survey

League of Women Voters

College Students

Civic Club Members

Risk Experts

Nuclear power 1 1 8 20

Motor vehicles 2 5 3 1

Handguns 3 2 1 4

Smoking 4 3 4 2

Motorcycles 5 6 2 6

Pesticides 9 4 15 8

X-rays 22 17 24 7

Food preservatives

25 12 28 14

Vaccinations 30 29 29 25

Estimated and Actual Death Rates Kammen and Hassenzahl)

Over-estimate risk of common and under-estimate risk of rare .

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How to Relate Risk?

Deaths per Ton of Coal Deaths per Number of Miners

NRC

Appropriate Unit of Measure of Risk? (NRC)

• From a national point of view, given that a certain amount of coal has to be obtained, deaths per million of tons of coal produced may be an appropriate unit of measure of the risk.

• From an exposed worker’s point of view, deaths per thousand persons employed may be more relevant.

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Choosing a Risk Measure (NRC)A few of the many ways risks of deaths have been measured:

• Deaths per million people in the population.• Deaths per million people within x miles of the source of

exposure.• Deaths per unit of concentration.• Deaths per facility.• Deaths per ton of toxic substance released.• Deaths per ton of chemical substance absorbed by people.• Deaths per ton of chemical produced.• Deaths per million dollars of product produced.• Loss of life expectancy associated with exposure to

hazard.

Loss of Life Expectancy (LLE)

Average amount that a life will be shortened by the risk.

If thousands of people are at risk, a few will die prematurely:

• Living in poverty (3500 days)

• Being male (vs. female) (2800 days)

• Cigarettes (2300 days)

• Being unmarried (2000 days)

• Being black (vs. white) (2000 days)

• Working as a coal miner (1100 days)

• 30 lbs overweight (900 days)

• Living in Southeast (350 days)

• Motor vehicle accidents (180 days)

• Dam failures (1 day) McKinney and Schoch

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Risks that Increase Chance of Death by One in One Million (10-6) (Kammen and Hassenzahl)

Smoking 1.4 cigarettes Cancer, heart disease

Drinking ½ liter of wine Cirrhosis of the liver

Spending 1 hour in a coal mine Black lung disease

Spending 3 hours in a coal mine Accident

Living 2 days in New York or Boston Air pollution

Traveling 6 minutes by canoe Accident

Traveling 10 miles by bicycle Accident

Traveling 300 miles by car Accident

Drinking 30, 12 oz. cans of diet soda Cancer causes by saccharin

One chest X-ray taken in a good hospital Cancer caused by radiation

Too little or too much of even healthful substances can be harmful (McKinney and Schoch)

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Spatial and Temporal Scales of Biological Organization (Suter)

Time and Scale of Environmental Concerns (Graedel)

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Ecological Risk Assessment (Suter)Scales of Observations in Toxicity Tests

Spatial Temporal Organizational:

Structural

Organizational:

Functional

Organism level

(laboratory-scale) cm3 to m3

Hours to days Organism Growth and reproduction

Microcosm tests

cm3 to m3

Days to months

Organism population, community, food web

Production cycling

Field tests

m2 to km2

Days to years Same as above Same as above

Environmental monitoring

m2 to km2

Years Same as above Same as above

Acute and Chronic Toxicity (Suter)

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1) Where did that Chemical Go? Fate/Mass Balance for Trichloroethylene (Suter)

2) Where did that Chemical Go?Mackay Fugacity Model for equilibrium partitioning of

chemical in different environmental compartments (Suter)

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Bioconcentration factor (BCF) (McKinney and Schoch)

3) Where did that Chemical Go? Exposure pathways (Suter)

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Combinations of Toxicants• Antagonism: substances work against each

other and partially cancel out each other’s effects (the use of antidotes, for example).

• Additivity: toxic effects are directly added (usually affecting different organs).

• Synergism: combined toxic effects are worse than adding individual effects together (smoking plus exposure to radon gas, for example)

Approach to Examining Risk (Kammen and Hassenzahl)

1) Take a broad view of the problem. This establishes a qualitative understanding of the mechanisms and usually identifies missing important information.

2) Use available data to arrive at a detailed quantitative solution.

3) Conduct sensitivity analysis to evaluate assumptions and need for better data.

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Living Area Radon Concentrations (pCi/L) (Kammen and Hassenzahl)

Radon Risk Calculations

• Living one’s whole life in a home containing 4 pCi/L of radon may be associated with an increased cancer risk of 10-6.

• Cancer Death Rate (CDR) = f(radon cancer potency, concentration, exposure time)

• Mean household radon concentration: 1.5 pCi/L• Time average person spends in a house: 15-18

hrs/day.• Radon cancer potency: 1 X 10-8 cancer deaths

per hour of exposure at 1 pCi/L.

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Problems with “Averages”

• What if 99% of all homes have negligible levels and 1% have very high levels?

• Louisiana: 0.28 pCi/L

• Iowa: 2.72 pCi/L

• Reading Prong, PA: 10 pCi/L

Sensitive individuals die at small doses, but tolerant individuals can survive large doses (McKinney and Schoch)

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Developmental Stages in Risk Management (Kammen and Hassenzahl)

• “All we have to do is get the numbers right.”

• “All we have to do is tell them the numbers.”

• “All we have to do is explain what we mean by the numbers.”

• “All we have to do is show them that they’ve accepted similar risks in the past.”

• “All we have to do is show them it’s a good deal for them.”

• “All we have to do is treat them nicely.”

• “All we have to do is make them partners.”

• “All of the above.”

Multiattribute Utility Analyses (NRC)• Method to formally bring multiple perspectives and

evaluations into a decision making process. • Especially useful for site selection (power plants,

airports, route selection, etc.) where conflicting objectives exist and many attributes must be considered.

• Quantifies subjective judgments from all interested groups.

• Ranks each option based on different viewpoints, using tradeoffs.

• Goal is to clarify positions and to test feasibility of various policy objectives, not to force a consensus through averaging.

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Life Cycle Analysis (LCA), or “Cradle to Grave” (McKinney and Schoch)

Green Technologies: Efficiency improvements, reuse/recycle, substitution (McKinney and Schoch)

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Customer Use Ratings for Car Comparison Example (Graedel)

Target Plots for Car Comparison (Graedel)

1950s Automobile 1990s Automobile

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Industrial Hygiene to Industrial Ecology (Pollution Prevention in a Big Way)

• 3M Company developed “Pollution Prevention Pays” (3P) in 1975.

• Goal to design pollution out of the manufacturing process (reformulating products, redesigning equipment, recovering and recycling wastes)

• Between 1975 and 1994, 3M saved $750 million in production costs and reduced air, water, and solid wastes dramatically.

Life Cycle Stages of a Manufactured Product (Graedel)Consider all stages, not just stage 2

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Industrial EcologyInstead of just designing processes that minimize waste, seek to design processes that use any remaining waste as the raw materials for other production processes:

1) Take as little as possible from the environment.

2) Use as much as you can of what you do take.

Industrial Ecology Flow Cycle (Graedel)

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Summary of Major Reported Infectious Diseases in Community Drinking Water Supplies

Reporting Period (Biannual) Average per Year

1989-1990 1991-1992 1993-1994

Agent Cases Outbreaks Cases Outbreaks Cases Outbreaks Cases Outbreaks

AGI 894 4 10,077 3 0 0 1,829 1.17

Giardia 164 1.83

Hepatitis 503 4 95 2 385 5 0.5 0.17

Escherichia coli O157:H7

243 1 41 0.17

Cryptosporidium 3,000 2 403,237 3 67,076 0.83

Campylobacter 172 1 28.7 0.17

Vibrio 11 1 1.83 0.17

AGI = acute gastroenteritis of unknown etiology

Summary of Reported Infectious Diseases in Foodborne Outbreaks

Agent Year Average per Year

1988 1989 1990 1991 1992

Cases Outbreaks Cases Outbreaks Cases Outbreaks Cases Outbreaks Cases Outbreaks Cases Outbreaks

Campylobacter 134 4 61 3 72 3 93 6 138 6 99.6 4.4

Escherichia coli 109 2 3 1 80 2 33 3 19 3 48.8 2.2

Salmonella 2987 94 4920 117 6290 136 4146 122 2834 80 4235.4 109.8

Shigella 3581 6 257 6 834 8 112 4 4 1 957.6 5

Staphylococcus aureus

245 8 524 12 372 12 331 9 206 6 335.6 9.4

Hepatitis 795 12 329 7 452 9 114 7 419 8 421.8 8.6

Listeria monocytogenes

2 1 0.4 0.2

Giardia 21 1 129 3 32 2 2 1 36.8 1.4

Norwalk agent 42 1 250 1 58.4 0.4

Vibrio (all) 49 6 6 2 2 1 11.4 1.8

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Kingston Fossil Plant - TVALocated at the confluence of the Emory and Clinch Rivers near Kingston, Tennessee.

One of TVA’s larger fossil plants. Consumes 14,000 tons of coal at full power.

Generates 10 billion kilowatt-hours of electricity a year (670,000 homes).

Plant construction began in 1951 and was completed in 1955.

Even in incidents such as these, risk assessment techniques can be applied to determine the likelihood of future problems and to determine which interventions are likely to reduce those risks.

What Happened at Kingston?

• Approximately 1 a.m. Monday, December 22, 2008, retaining wall on ash pond collapses. (last annual inspection, October 2008)

• 60 acres of ash (out of 84 acres) released. This is approximately 9.4 million cubic yards.

• More than 8 and less than 15 homes impacted. However, several were flooded and at least one was knocked off its foundation and moved.

• Flooded nearby roads and railroad tracks.

• Estimated 4 - 5 ft of water over 250 - 400 acres.

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Aftermath of Earthen Dike Failure

• Dead shad found in river (some state this may be a result of freezing temperatures that morning, which also likely contributed to wall failure).

• Metals of concern include arsenic and mercury, plus many others.

• Massive cleanup, including temporary damming of nearby river to contain flow.

• NOTE: Ash pile has at times been more than 55 ft above water level in pond.

• Use Risk Assessment to determine the potential for contamination and resultant health problems from arsenic and mercury.

Conclusions• Unaware we are taking numerous significant risks, or we

accept them due to their familiarity.• We artificially elevate risks for uncontrollable and

unobservable outcomes.• Can evaluate options to minimize, but not eliminate,

risks.• Life-cycle analyses and pollution prevention have

prevented tremendous amounts of wastes from being discharged and have dramatically reduced energy and other inputs in many industrial processes.

• Tremendous potential to further reduce risks and discharges with widespread application of pollution prevention concepts.

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Main References

• Graedel. Streamlined Life-Cycle Assessment. Prentice Hall. 1998.

• Kammen and Hassenzahl. Should We Risk It?Princeton. 1999.

• McKinney and Schoch. Environmental Science Systems and Solutions. Jones and Bartlett. 1998.

• National Research Council. Understanding Risk; Informing Decisions in a Democratic Society. National Acad. of Sciences. 1996.

• Suter. Ecological Risk Assessment. Lewis. 1993.