163 Análise de Riscos

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ENVIRONMENTAL HEALTH RISK ASSESSMENTS
SCIENCE OR VOODOO?
Ron Pearson, M.S., CIH
Environmental Health & Safety, Inc.
St. Paul MN
EH&S, Inc.
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The Nature of Risk
200 people die annually in U.S. from electrocution (risk level 10-6 per year)
should I replace the wiring in my old house?
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The Nature of Risk
7000 people die annually in U.S. from falls in their homes
but ... most are over age 65, so should the rest of us ignore this?
It's all about CHOICES
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Estimating Risk
Probabilities are fine until it happens to me
Some of the uncertainty is due to chance, some of it isn't
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Estimating Risk
Historical risks are easily understood - e.g. car accidents
What kind of car do you drive?
Does it have airbags?
Do you drive fast?
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Comparing Risks
action annual risk uncertainty
all cancers 3 in 1,000 10%
pack-a-day 4 in 1,000 150% smoker
mountain 6 in 10,000 50% climber
car accident 24 in 10,000 10%
drinking MCL 6 in 1,000,000 1,000% of chloroform in water
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Comparing Risks
Human nature dictates that we tend to worry more about risks that are severe and abrupt, as opposed to something that has some "probability" of occurring down the road
Many say that we “can’t” compare unlike risks, but in fact, we do it all the time
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The Costs of Risk Reduction
Location Risk Reduction Cost per (geog.) means life saved
Indonesia Death Immunization $100 countries (infection)
U.S./ Cancer Pollution $1,000,000 other prevention
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Why do we need Risk Assessment?
"Emerging" risks - e.g. hormonal analogues
Shifts in perception
information overload - the "health studies" results that we are bombarded with daily
ability to measure minute amounts of substances
many traditionally severe health risks (e.g. smallpox) are gone
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Environmental Health Risk Assessment
health risk = the likelihood that an adverse effect will occur to a person (or group of persons) in a chemical exposure situation
Usually, a higher exposure causes more serious effects or makes them more likely
At some low exposure level, the risks become insignificant
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Estimates of Risk
Estimates of risk are needed to assist in making decisions
Only in extreme cases will risks estimates alone drive decision making
zero risk compels no action, while a great risk may compel immediate action
IN REALITY, risk estimates lie somewhere in between
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Environmental Health Risk Assessments use two types of Risk Estimates:
for carcinogens, the increased probability of individuals' getting cancer from a particular exposure
for other toxicants, a comparison of expected exposure to an exposure that is assumed to be insignificant
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Environmental Health Risk Assessments use two types of Risk Estimates
Why? Because they are most often used in USEPA risk assessments
In general, effects on systems such as the reproductive or immune system are not scrutinized nearly as much as carcinogenic effects
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What DON’T risk assessments estimate?
total number of people affected
relative incidence of an adverse effect in populations known to be exposed with those not exposed
the ratio of the expected risk with the exposure to that expected without it
reduced life expectancy associated with the effect
lost income potential, costs to society
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Uncertainties in Risk Assessments
Dose Effect = relationship between the amount of a chemical exposure and the nature and/or severity of the toxic effect
Data on toxic chemicals usually come from:
laboratory experiments on animals NOT epidemiology studies of humans
moreover, many are inferences based on bacterial and/or human cells
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Uncertainties in Risk Assessments
Dr. Bruce Ames, (Ames salmonella microsomal screening test developer), stated repeatedly that he never intended for his "tool" to be applied as it is today
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Uncertainties in Risk Assessments
both of these sources of data cause problems because:
 an animal or cell is not a human being
 most animal toxicity data is short-term 
 relatively high exposures are used experimentally, to cause statistically significant effects
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Uncertainties in Risk Assessments
many species are homogeneous (purposely, to limit variability in response)
By contrast, humans are diverse in their response to chemicals due to:
genetic make up
age
habits
occupation
health status
diet, etc.
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Uncertainties in Risk Assessments
some argue that extrapolations from animals to humans are more reliable than epidemiology studies, due to:
small study populations (lack of "statistical significance")
confounding variables
lack of exposure data
differences between study populations and the population to be protected
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Uncertainties in Risk Assessments
When no effect is seen in lab animals, is there negligible risk to humans exposed at such a level? 
a 1% incidence of any disease would be impossible to detect in a study of 25 animals, but would represent more than 2 million cases if the entire U.S. population were exposed
HOW DO WE ANSWER THIS QUESTION???
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Uncertainties in Risk Assessments
In risk assessment, it is often assumed that:
for cancer: there is no safe dose, and;
at low doses, the relationship between dose-effect is directly proportional (linear)
for other health effects: there is a safe dose
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Public Perception and Public Demands
The "vicious circle":
public perception -> media reporting -> congressional action -> agency regulation in response to public demands
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Public Perception and Public Demands
Are we (in the U.S.) better off now than before the "skyrocketing" industrial use of chemicals?
Since 1940 - life expectancy has increased nearly 15 years
Since 1970 - infant mortality has decreased by 1/2
Since 1970 - heart disease has dropped by nearly 1/3
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Public Perception and Public Demands
Cancer deaths have increased...or have they?
Many feel the this is due simply to:
 smoking (increases lung, pharyngeal, pancreatic and bladder cancer incidence)
sun exposure (malignant melanoma has increased eight-fold)
the increase in life expectancy (you have to die of something...)
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Where has this all brought us?
Many times, the science of epidemiology simply confirms the obvious - rarely has an epidemiological study drawn attention to an agent that was not already recognized by an astute observer in the field (e.g. Fen-Phen)
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Where has this all brought us?
We fear carcinogens in our drinking water ... but what about Milwaukee's public water supply and an outbreak of cryptosporidium? Would we better off taking some of our money from the former and spending it on the latter?
Asbestos: we won't even get into it ...
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Regulatory “Reform”
What agencies conduct health risk assessments? 
OSHA
EPA
FDA 
USDA
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Regulatory “Reform”
1983 - the NAS published the "Red Book" - "Risk Assessment in the Federal Government: Managing the Process" 
 defined four steps of risk assessment, but more importantly, discussed how to separate the "science" from the "policy"
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Regulatory “Reform”
1987: EPA published "Unfinished Business" - ranked
items such as pesticides in food and radon as higher health risks than items such as groundwater contaminants or hazardous waste sites BUT...failed to rank airborne lead as a high risk - again, it was driven by carcinogens....essentially we have no scientific methods for comparing cancer with non-cancer risks
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Regulatory “Reform”
1991 - Federal Focus, Inc. called for an executive order (16 CRR 171), essentially prohibiting the use of overly conservative assumptions
Risk Assessment has been represented by many as a "value free" process, when in fact it is full of judgements
Risk Assessment and Risk Management are, and should remain, separate processes
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Regulatory “Reform”
Risk Assessment produces very precise numbers of questionable accuracy
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Regulatory “Reform”
Federal Trend: legislators pursuing risk assessment as means of telling us what the "real" risks are, so we can spend our money accordingly - represents another easy answer for attacking what ails us - after all, what politician in their right mind would outright oppose legislation that is supposedly "good for the environment"?
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Regulatory “Reform”
State Trends: decreasing funding for public health/environmental health programs but increasing environmental regulatory spending - in 1994 we spent $4.09 per capita on the former and $18.87 per capita on the latter
In the Republican party's "Contract with America" a bill called the "Job Creation and Wage Enhancement Act" bolstered risk assessment and cost benefit analyses requirements
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Cost-Benefit Analysis
A good example of cost-benefit analysis and the fallacies that can be put forth:
OSHA's proposed IAQ rule estimated that a facility manager would spend an average of 15 minutes documenting each complaint
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"Advancements" in the Science of Environmental Health Risk Assessment
ASTM RBCA - Risk Based Closure Assessment methodology
many states have jumped on the bandwagon for this approach to screening UST sites, especially as state funds have become more scarce
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ASTM RBCA - Risk Based Closure Assessment methodology
uses a tiered approach
Tier I: "lookup tables" 
Tiers 2 - 4: incorporate more site specific values for:
ground water
soil types
specific information on receptors
Still, much of the conclusions depend on mathematically modeled results - "garbage in - garbage out" still applies
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Conclusion: Where do we go from here?
Most environmental problems are extremely complicated technically
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Conclusion: Where do we go from here?
We live in the age of entitlement: we want the government to provide us a risk-free society, and we want it now!
We MUST decide how much minuscule reductions in risk we are willing to pay for
We MUST question our legislators AND regulators motives and actions
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Conclusion: Where do we go from here?
We live in the age of technology, and science can solve all of our ills: modern science has it's limitations, particularly when it comes to the analysis of living systems - it may never suffice in accurately predicting health effects or their potential from low level exposures
 We MUST decide how much uncertainty we are willing to tolerate
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Conclusion: Where do we go from here?
We live in the age of the sound byte: most of the public gets the lion's share of this information from the media 
We MUST improve communication of these issues dramatically
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Conclusion: Where do we go from here?
We live in the age of cancer paranoia: most of the EPA's regulatory efforts focus on cancer
 We MUST shift the emphasis equally to non-cancer endpoints
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"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoidance of danger is no safer in the long run than outright exposure. Life is either a daring adventure, or nothing."... Helen Keller
“DON'T WORRY - BE HAPPY” ... Bobby McFerrin