Topic: Question Set 1. Question 10. Risk Strategies & Levels of Toxicity

Subject: Question Set 1. Question 10. Risk Strategies & Levels of Toxicity Posted: Mar-04-02 at 4:04 PM by Kenneth Campbell

10. What distinctions might be made between lethality, morbidity, reproductive capacity, quality of life, and quality of environment impacts vis a vis risk assessment strategies?

Posted: Feb-12-03 at 12:11 PM by Erin Valentine

10. The distinctions between these categories of various levels of risks and the risk assessment strategies are that of result of exposure to a particular toxic substance. Assessing the risk of a lethal substance would include animal testing and determination of LD50 under a varying set of conditions, such as length of exposure, site of exposure, number of test subjects, etc. Assessing the risk of a morbid agent would require more specific testing. The observations would now have to include clinical observation of symptoms and postmortem examination to determine the site of action and characterization of the specific effect of the chemical. These observations may be the occurrence of tumors, damage to particular organs, or interruption of a biological function. In the case of assessing the risk to reproductive capacity, the tests must focus specifically on the endocrine and reproductive systems of the organisms. The tests to determine the reproductive toxicity of an agent are performed on rats through six stages described by the International Commission on Harmony, from premating to weaning and sexual maturity of the offspring (Klaasen 2001). Quality of life risk assessment would need to test the ability of the agent to affect a condition of life that does not cause death or disease such are skin and eye irritants. Quality of environment impacts risk assessment must test all of these conditions as well as the effect of the agent on the natural habitat. This assessment might include the effect of an air pollutant on the human population (lethality, morbidity, reproductive capacity, quality of life) and on the wildlife (LD50 of certain populations) and on the plant life (observation of decrease in growth).

Posted: Feb-14-03 at 9:58 PM by Lisa McIntosh

On an individual basis, the first three terms reflect varying degrees of toxicity: lethality, obviously, is the most severe; morbidity may ultimately decrease lifespan; reproductive capacity in and of itself may not adversely affect an individual, although could negatively impact a population through decreased fecundity.

Quality of life impacts may not necessarily result in harmful effects to an organism; however, that quality is degraded from optimal conditions. Nuisance odors- chemicals present at concentrations above the odor recognition threshold, but below deleterious levels-are a good example of this. In terms of risk characterization (in Massachusetts, anyway), the presence of nuisance odors indicates a condition of significant risk to public welfare exists (even if the contaminants may not present a risk to human health).

Quality of the environment, be it on a localized or global scale, ultimately determines the level of impact. Risk assessment is a tool by which we relate the quality of the environment to public health or the environment. The underlying premise is that there is an "acceptable" level of risk—such as allowing residual contamination to remain in the soil, using a drug for therapeutic effects despite the potential for side effects, or using household cleaners or pesticides that may be lethal if used incorrectly.

Posted: Feb-16-03 at 12:03 PM by ERIC FAULKNER

Risk assessment can be classified as a quantitative estimate of the potential effects on human health and the environmental significance of various types of chemical exposure (Klassen). In identifying a hazardous agent, tests are performed to determine if the agent will cause an adverse effect through structure activity analysis, in vitro testing, animal bioassays, and epidemiology studies. Additional testing is performed to determine the dose-response relationship and the duration of exposure to the hazardous agent in question. These assessments form a Venn diagram that make up the three categories of toxicological studies; mechanistic, regulatory, and descriptive. While lethality, morbidity, reproductive capacity, quality of life, and quality of the environment all play significant roles in the study of toxicology, further distinctions can be made by the following; lethality is an acute test first performed on a NCE with a fixed dose on a small population where an LD50 is determined. Morbidity can be considered a long term exposure study where a population is subjective to an agent for greater than 3 months where alterations on biological functions are addressed. Reproduction takes into consideration the effects of the reproductive system and the potential of the hazard to disrupt embryonic development. And furthermore, quality of life and quality of the environment assess the effects of a hazard on a large population and in nature where risk managers summarize the potential risks.

Subject: Re:Question Set 1. Question 10. Risk Strategies & Levels of Toxicity Posted: Feb-17-03 at 1:29 AM by Michael George View the history for this message Reply Edit the message Re:Question Set 1. Question 10. Risk Strategies & Levels of Toxicity Delete the message Re:Question Set 1. Question 10. Risk Strategies & Levels of Toxicity

Looking at individuals, lethality which leads to death, morbidity which leads to a decrease in lifespan, and reproductive capacity all are the most serious. The last one could end up affecting a population as a whole in the long run. Quality of life toxicity issues wont necessary affect the organism in harmful ways, but may cause degradation in the quality of life for the organism. For example a annoying smell may occur in the organism or a scar which may be unpleasant but won't probably lead to death. But, the presence of an odor in an area may lead to fears of something harmful even though there is no harmful toxicant. Quality of environment is looking at the safety of the environment as a whole. It is important for risk assessments because it allows us to keep the public informed to what is a safe level of risk for products that are toxic such as household products. Also in what are side effects for medicines.

Posted: Feb-17-03 at 7:09 PM by DINA KATZ

A risk assessment is an expert's opinion of the likelihood of a deleterious effect. Depending on what that effect might be, lethality(death), morbidity(disease), quality of life (level of comfort for the living organism), etc., the assessment will differ for the same toxicant. There may be a high risk of reduction in the quality of environment (how conducive the surroundings are to life) but not necessarily lethality. For example, an oil slick is a high risk for the beach by your house, but it carries a very low risk of death for you personally. Similarly, reproductive capacity of pond-living organisms may be severely reduced by a toxicant dumped into their pond, but have no effect on their own quality of life. Assessment strategies would thus have to be tailored to estimate the risk to a specific effect (i.e. if it is necessary to carry out an assessment of morbidity of tadpoles in Lake Erie, one should probably observe behavior and collect some specimens and inspect their tissues, rather than spend time observing a reproductive cycle and counting young.)

Posted: Feb-18-03 at 4:23 PM by Ivana Djuretic

Risk assesment strategies require the following components:

-hazard identification-an evaluation of the adverse health effects the agent is capable of causing: damage to liver, nervous system, carcinogenesis

-dose response assessment-includes prediction of exposure levels at which risk is likely to be negligible or nonexistent

-exposure assessment - a determination of how much of an agent people might be exposed to under various conditions such as use of a drug or a consumer product, environmental exposure at a hazardous waste site.

-risk characterization- explicit description of the assumptions and uncertainties that go into the risk assessment, and the overall confidence in the results of the analysis.

It seems like risk assesment strategies will only characterize lethality of a substance with a high degree of certainty (even then there is genetic variability) but that for other levels of toxicity it will be extremely hard to predict the levels of risk. Even for a simpler task such as cancer assessment, mathematical models are needed to connect the results of experiments with a limited number of animals to large scale predictions (more than 1 additional cancer in 1 million exposed people is unacceptable risk, but you cannot test 1 million animals). So morbidity, reproductive capacity, quality of life and environment differ from lethality in the certainty of risk predicted by risk assesment strategies.

I will use this question to comment on the ambiguity of the assigned questions (some, not all). I found it really hard to formulate an answer to this question without just defining what lethality, morbidity etc is, or giving the type of tests that one would do to assess lethality, morbidity, etc, but that doesn't seem to be what the question asks. Even after reading Ch 4 and doing some additional research I couldn't describe in one simple answer how risk assesment strategies would distinguish between all those different categories of toxicity. The answer seems to be the entire of toxicology. Is anybody else having problems with the nature of the questions? Maybe we are unable to start threaded discussions because people are interpreting the questions in different ways and its hard to agree or disagree with someone talking about an entirely different thing than yourself. Again it could be just my view, but I'm almost sure that having more specific questions would spark a discussion less vague.

Posted: Feb-20-03 at 10:29 PM by Diana Esshaki

The variety of adverse effects of chemicals on humans clearly impacts risk assessment strategies. Bioassays and LD50 aid in developing these strategies. When assessing risk of toxins, lethality (ability to cause death), morbidity (ability to cause disease), reproductive capacity, quality of life, and quality of envronment do have distinct impacts on determining risk. In this case, since the question is quite vague, it is probably more helpful to look at an example: mold spores.

(Radiation is actually a more clear cut example, however, I am assuming that we aren't considering that a toxin.)

Lethality: Clearly the most significant factor does not play much of a role with mold spore exposure. Put another way, when assessing risk, this "toxin" does not cause death.

Morbidity: Exposure to mold (esp.indoor constant exposure) can cause a wide array of health problems. Very large doses of mold spores (inhaling or ingesting) can result in poisoning by mycotoxins. Exposure can cause allergic illnesses, asthma, and infection (lung or respiratory tract). In this case, morbidity has a very high and quite distinct effect on risk assessment.

Reproductive capacity: Mold spores are not usually a health risk factor on repro.

Quality of life: Mold spores indoors can not only cause a health risk, but can make living uncomfortable by adhering to ceilings, etc. in the home.

Quality of environment: Varies depending on indoors vs. outdoor exposure- indoor causing more direct inhalation and infringing on safety of the individuals exposed.

Old

Allison:

February 20, 2002

10. Risk assessment strategies are definetly impacted by differences between lethality, morbidity, reproducing capacity, and quality of life and environment. In determination of the risk of a toxin, acute testing would be performed on toxins that my be considered lethal. Morbidity involves a compromise of function, including, disease rates, genetic defects, and toxicant effects, all of which may not be lethal. In testing whole populations, reproductive capacity and morbidity may lead to lethatlity, which is very damaging and would be considered in those risk assessments.

However, when looking at individuals rather than a species as a population, morbidity , reproducitve capacity, as well as, quality of life and environment may not be extrememly toxic in the sense that one can still survive. Toxic effects exist at various levels and when assessing risk of a toxin, it is possible that they will not induce effects that generate lethality of morbidity but will alter quality of life and/or environment. In these cases, the strategy about how assess risk changes and preventing death is no longer a goal, but instead preserving a quality of life and

general well being.

Joanne:

February 20,2002

10) Lethality: death

Morbidity: diseased state, decreased life span

Reproductive capacity: ability to reproduce

Quality of Life: nonmedical threats that compromise one's ability to enjoy life

Quality of environment: degree of safety, comfortability and security in surroundings

In terms of these factors with respect to risk assessment strategies, they are ordered in terms of

importance with the greatest stressor on lethality and in descending significance thereafter.

Obviously,lethality would have the greatest influence on risk assessment. Although there may appear to be an element of subjectivity (ie reproducitve ability vs quality of environment..etc..etc), overall they are ranked in accordacne with what the majority of individuals would assess in terms of personal importance.

Neetu:

February 20, 2002

10. Lethality is related to death, morbidity is related to compromise in functionality. In individual lethality, it is not necessary that it means inability to reproduce. When talking about population lethality, th emorbidity might be lethal. The toxins might change one;s quality of life or living standards but it is not necessarily lethal. The quality of environment will effect each individual differently.