MPH 605Environmental

HealthLecture #3

Dr. Sylvia Hood Washington

Monday, April 12, 2010

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TOPIC Risk Assessment

1.Risk Assessment

2.Environmental Health Risk Assessment Process

3.Risk Management

4.Dose-Response Modeling

5.Uncertainty Analysis

6.Criticism

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Risk Assessment

•Risk assessment is the process of identifying and evaluating adverse events that could occur in defined scenarios.

•As per Kaplan, risk assessment is trying to answer three questions:

1. What can happen?2. How likely is it to happen?

3. What are the consequences if it does happen?

Environmentally, risk assessors focus on health impacts that may occur from exposure to particular agents, from …

1. the workplace,2. living environment or

3. from visiting a particular environment

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The framework for environmental health risk assessment was created in 1983 in a National Research Council

Report, Risk Assessment in the Federal Government, which is commonly referred to as the red book. It

divides risk assessment into four elements:

1. hazard identification2. dose-response assessment3. exposure assessment and

4. risk characterization.

Environmental Health Risk Assessment Process

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1. Hazard Identification

This is the process of identifying and selecting the environmental agent and health effect for

assessment.

The process includes causal inference for particular health outcomes that is based on

toxicological and epidemiological evidence for causation.

The scope of inquiry can be one agent and one health affect or the scope can be much broader.

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2. Dose-Response Assessment

This element of the risk assessment process attempts to describe the quantitative relationship between exposure and disease.

A mathematical model is developed (or selected) and is used to predict the level of toxic response for any dose.

These models can also be used to adjust for different factors such as gender, species, race, etc.

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Dose-Response Modeling

Dose-response determine interpolations between tested doses. Model selection should be based on biological considerations and well-characterized mechanisms of toxicity.

The multistage model postulates that a sequence of k critical sub-cellular events (mutation, changes in gene expression or cell proliferation) must occur for transformation form a normal cell to a tumor.

Mechanistic, biologically based or biologically motivated dose-response models attempt to model the dose to disease process in more detail. The hope is that it will provide a better understanding of the true shape of the dose-response curve and better basis for extrapolating results from lab animals to humans.

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Monotonic dose-response models can be expressed using a simple concept that is known as tolerance distribution.

1. Assumes that each individual has a specific tolerance for a certain toxicant and when exposed at that level or above, the disease will develop in the individual.

2. The opposite will occur if the exposure level is below the tolerance and the disease will not develop.

Dose-Response Modeling

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3.Exposure Assessment:

This includes the estimation or measurement of the:

1. magnitude

2. duration

3. timing of human exposures of the agent of concern.

The routes of exposure and exposed populations are required to complete the exposure assessment.

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4.Risk Characterization:

Finally, risk characterization consists of combining the information from the other steps in order to estimate the level of response for the identified health effect at the specific level of exposure to the specified agent for the defined population.

Mathematically, the risk is calculated by substituting

the specific dose amount into the dose-response equation to compute the response level.

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Risk Management

1. De Minimus Risk: This is the idea that some risks are so small that that they are acceptable or insignificant from a societal perspective.

2. Risk-Benefit Analysis: Sometimes risk is the result of activities that are otherwise beneficial that is why it is important to make risk assessments while taking benefits into account.

3. Cost-Benefit Analysis: This type of analysis is always a concern and is a requirement of certain environmental health regulations.

4. Decision Analysis or Alternatives Analysis: Obviously, the best decisions are made after considering all the relevant potential consequences rather than focusing on only particular consequences.

5. The Precautionary Principle: This idea suggests that serious risks should be avoided or mitigated when possible, even when those risks are unlikely or uncertain. It is most useful for situation where little information is available.

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Uncertainty Analysis

There are two approaches to such analysis: internal and probabilistic.

1. Internal: This approach is to estimate the risk twice, once using best-case parameter estimates and then again using worst-case parameter estimates. The advantage is that it is simple, easy to explain and potentially provides useful quantitative information. The disadvantage is that it provides no information about the relative plausibility of individual risk estimates within the interval.

2. Probabilistic: This approach describes risk using one or more probability distributions indicating the plausibility of an entire range of risk estimates. It has been argued that the relative plausibility of an entire range of risk estimates is impossible to determine reliably and that such attempts may mislead and confuse risk managers and stakeholders.

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Criticism

1. Controversy often arises over:• the use of conservative default assumptions in exposure

assessment and dose-response assessment• the inadequacy of data and models for assessing affects• … and the wisdom for basing policy decisions on highly uncertain

risk estimates.

2. It is challenged because of the judgments, the untested hypotheses and the default values that are relied on in the absence of clear evidence.

In summary, risk assessment is susceptible to criticism because it is an attempt either to estimate unmeasured past or present or to

predict an unknown future.

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Exposure Assessment

Exposure Assessment, Industrial Hygiene and Environmental Management

Discussion Topics

1.Industrial Hygiene vs. Exposure Assessment2.Anticipation, Recognition, Evaluation and Control

3.Exposure Assessment

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Industrial Hygiene vs. Exposure Assessment

Industrial hygiene and exposure assessment share a common task: quantifying hazardous exposures. However, they approach

this task in different ways.

1. An industrial hygienist would typically monitor air levels of hazardous solvents and if they were excessive,

solutions would be implemented.

2. An exposure assessor would specialize only in measuring and quantifying exposures and responsibility for

controlling excessive exposures would rest with other professionals.

Anticipation

1. Anticipation can be thought of as the pre-preliminary assessment made prior to going into the field. Prior to being in

the field, information is reviewed and a preliminary list of potential health and safety hazards can be developed.

2. Traditionally, an industrial hygienist is called upon to evaluate safety hazards such as chemical storage that poses a threat of fire or explosion, health hazards such as high noise levels or

elevated temperatures (physical hazards) as well as acute high level exposure to highly toxic chemicals such as chlorine gas

(chemical hazards).

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Anticipation, Recognition, Evaluation and Control

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Recognition1. The initial recognition of the hazards is completed through a visual inspection (site visit or walk-through) of the facility. The purpose of the visual inspection is to gather both qualitative and quantitative information about the occupational and environmental hazards associated with the facility.

2. As the walk-through or site visit is being conducted, recognition of the sub-populations is also occurring.

3. Different groups of the facility may be exposed to different hazards (ergonomic hazards as opposed to heat stress).

4. At the conclusion of the visual inspection, the goal is to have a detailed picture of the manufacturing processes and of the associated hazards as well as a plan for evaluating these hazards.

5. The plan is to be in writing and the next phase, evaluation can be started

Anticipation, Recognition, Evaluation and Control

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Evaluation

In small facilities or where required, a census sample is taken and then all potentially expose individuals are monitored. And last, a third population, the anecdotal or convenience sample is used. This sample consists of volunteers or individuals with particular complaints. Such sampling is subject to bias and should be avoided.

There are two types of instruments available for measuring environmental exposures; they are direct reading instruments and sample collection instruments.

1. Direct reading instruments are useful for measuring physical hazards, such as temperature, noise and radiation. They can also be sued to measure levels of many airborne pollutants (gases, vapors and particles).

2. Sample collection instruments are used when multiple airborne pollutants are present or further analysis of samples is desirable.

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Control

The hygienist can take several approaches to changing the workplace through substitution, isolation and ventilation.

1. Substitution involves replacing a hazardous material or process with a less hazardous one.

2. Isolation involves containing or limiting access to the hazardous process.

3. Ventilation (introduction of fresh air, local exhaust ventilation or introduction of cool air to a hot location) is used for certain hazards such as chemical or heat-related hazards.

Protective devices are used to control safety hazards. Personal protective equipment such as respirators, safety glasses or hard hats may also be recommended.

Another option available for control is through administrative strategies. For example, rotating workers through dangerous jobs will limit an individual’s aggregate exposure.

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Time course is an important factor of exposure because some contaminants are relatively readily metabolized at low levels of exposures but toxic at higher levels of exposure. As such, the dose rate may affect the health outcome.

To account for such differences, exposure assessors focus on magnitude, frequency and duration.

Exposures are also characterized as acute or chronic exposures.

1. Chronic exposures occur over months, years, or even decades and at low levels may manifest non-acute health outcomes.

2. Acute exposures are brief and when they occur at high levels, poisoning or other acute responses may follow.

Exposure Assessment

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There are three principal routes of exposure for contaminants to enter the body: 1. inhalation2. ingestion 3. dermal contact. These are different from the exposure pathway, which is the path by which the contaminant moves from one source to a human receptor.

Routes and Pathways

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1. Researchers use indirect exposure assessment methods that forgo direct measurements of the exposures of interest or that use partial data.

2. Another method is called exposure scenarios in which an activity pattern for an individual is assumed and available data is used to make estimates.

3. Indirect exposure assessment is also made through a process called job-exposure matrix.

Assessment Methods

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Measuring Environmental Exposure

Constant measuring occurs to allow for detailed exposure information which can be used for public education/warnings, to monitor the success of interventions and to support public health research.

Assessment Methods

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This involves outfitting an individual with monitoring

equipment that measures the exposures that occur during daily

activities. It allows for exact exposures to be measured and

assessed.

Assessment Methods

Measuring Personal Exposures

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Ingestion1. One approach is to collect duplicate portions of food that is eaten and complete an

analysis or duplicate diet study.

2. Second approach is to have individuals keep dietary journals. The same foods will be purchased and brought to a lab for analysis.

Skin Absorption: This is much more difficult to measure.

3. One method is to have individuals wear a patch on the skin where absorption of the material of interest occurs.

4. Another method is to use the skin of a cadaver.

Assessment Methods for Ingestion and Skin Absorption

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Measuring Biomarkers:

In order to measure the exposure levels in an individual is through the use of biological markers.

Same biological material such as feces, hair, exhaled breath, urine or blood is gathered and used for analysis of actual human exposure.

Assessment Methods

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In the US, occupational injury death per year is between 5,000 to 6,000 however, occupational illness leading to death is

49,000 to 65,000 per year.

Globally, the data gets worse as more hazards are introduced in poorer nations.

In the poorest of nations not only are the hazards greater but the lack of data is a

significant issue.

Workplace Environments

As the world’s economics changes, the nature of work is changing. Nevertheless, there are still plenty of workplace hazards.

While the hazards from a job such as mining seem obvious, there are occupation hazards that pose threats not as obvious but just as hazardous.

For individuals such as undocumented farmers or those working in the streets, the long hours are probable, hazards are uncontrollable, injuries/illness are probably great and labor laws are probably few.

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Varieties of Workplace Environments

According to the ILO (International Labour Organization) ~50% of the world’s population (2.84 billion) people are engaged in economic activities

Time of work hours/year varies between 1,421 (Germany) to 2,316 (Korea). US =1,792 hours (2007)

Developed Countries: Service sector , industry, 10%-agriculture

Transitional Economies: Agriculture, services, industry

Agriculture worldwide is no longer the dominant employment—Service is.

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Workplace Health and Safety

The following are some of workplace health and safety issues:

Occupational lung disease (miners breathing asbestos, carpenters breathing in dust)

Acute injuries (construction, transportation, mining, agriculture).

Disorders of reproduction (pesticide use).

Noise-induced hearing loss (machinists, carpenters)

Infectious disease (HIV, airborne infections for health care worker, also at risk are those who are in contact with animals such as slaughter house workers)

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Injuries and Illness Data

To determine whether or not occupational health is a public health issue, experts turn to available data. Main sources of such data are from employer reports and insurance reports. Other sources of data are workers compensation systems and insurance companies.

The downside to relying on data is that much goes underreported and we are forced to seek additional sources of data. Such sources are health care systems (ER data), vital records such as death certificates, police/justice system reports and trauma registries.

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