Basic Environmental Health - Assignment Example

Introduction to Environmental Health Sciences Basic Environmental Health Parathion Case Study, Epidemiology, Risk Assessment In the parathion casestudy, a variety of field measurements were made to assess worker (volunteer) exposures to the OP pesticide. Name three types of field data that were collected in this study. For each data type, describe what information it contributed to the exposure assessment, and describe at least one limitation of the data. Example: Field data type: Urinary metabolites of parathion (DEP and DMP) collected from study participants Information gained/limitation: The urinary metabolites were used as biomarkers of exposure, providing estimates of parathion/paraoxon exposure from all routes. The main disadvantage of the measurement is that multiple urine collections must be made between 12 hours and 3 days post exposure to completely quantify exposure using this technique. Another limitation is the relatively high cost of the analytical methods involved, and therefore the small number of subjects whose urine could be monitored. Field data type: Both the garment and patch samplers of the mixers and applicators were used to extract the pesticide from these coverings and then used for quantitative analysis (Spear 2006). Information gained/limitations: Whatever a worker wears at work place either an apron to cover the body or gloves to protect hands or even a patch applied to skin, they all are protective coverings and hinder the contact of parathion with the skin/body. So parathion is kept on these covering materials. Through these measurements the quantity of pesticide present on these materials is estimated and gives an average dose of parathion present on these coverings. At times these estimates may change due to: a) spillage of the pesticide, b) change in the temperature and climate, which affects the vaporization of parathion. These measurement errors are controlled at the time of calculation of final dose of the pesticide which would have been on the skin if these protective measures had not been taken by covering the body (garments, gloves, etc). These calculations are made by utilizing an amount of parathion (in mg) present on the skin (surface area) for a certain period of time (hours) (Spear 2006). Field data type: The filter removes the pesticide from the inhaled air. The weighted average air concentration is estimated through a product of duration of exposure, respiratory rate and the quantity of parathion, inhaled in out of total air, collected by the filter. The quantity estimated is inhaled mass of parathion (Spear 2006). Information gained/limitations: Some of the sampling devices have been used in the estimation of respiratory exposure like, pump and mask with filter. This pump is affixed to the worker’s belt, which draws air from the breathing zone through a filter, which separates the particulate aerosol from the air stream. Each worker wears this device and the quantity found on the filter is estimated. There are chances of some errors to occur during the estimation procedure because: a) size of the aerosol is important for its passage through airways up to lungs, b) variation in respiratory rate and, c) variation in depth of respiration at different occasions in different individuals (Spear 2006). Field data type: Blood samples collected from the mixers/applicators or field workers with cholinesterases in both erythrocytes and serum (Spear 2006). Information gained/limitations: Cholinesterase, found in red blood corpuscles or serum, is used as an important marker of organ phosphorus compound poisoning. This enzyme is used in routine monitoring as well as in acute exposure to these poisonous compounds. There are some limitation to this method and should be kept in mind while interpreting the results, like: a) there may be variation in the same the individual at different times, b) variation between different individuals, c) the assay used for the measurement purpose may also give different results as compared to other assay used (Spear 2006). 2. a. People who load/mix parathion, people who spray parathion onto crops and people who harvest crops treated with parathion are all potentially exposed to the compound. For each of these three groups of potentially exposed people, describe the form(s) of the compound they are likely to be exposed to. (For example, dilute or concentrated? Parathion or paraoxon? Liquid, aerosol or residues?) For each group, name one potential step they could take to prevent exposure and/or minimize continued exposure once it has occurred. *Information required *Loader/Mixer of parathion *Sprayer of parathion *Harvester of parathion Exposure to compound Concentrated Diluted Diluted Parathion Paraoxon Paraoxon Liquid/aerosol Aerosol/residues Residues Protective measures Full body clothing (apron) with gloves, long shoes and mask Mask, gloves, long shoes, if possible full body clothing Mask, gloves, long shoes *Source: Spear 2006 b. What experimental evidence (data) collected in the parathion field studies suggested to the researchers that the dermal exposure route was more important than the inhalation route? Explain your answer. Dermal route is important because skin may come in contact with any pesticide in all its forms including solid, liquid or vapors but for the inhalational route to be utilized the chemical has to be in the shape of vapors. Gastrointestinal route may also be utilized when there is unintentional ingestion of the chemical through sold or liquid. Parathion is more toxic and concentrated before it vaporizes so when a worker handles parathion his/her skin is exposed to all its forms. As far as parathion is concerned, it gets diluted in the air and its effects are decreased if it inhaled. Moreover, Spear et al showed that dermal route was important as far as the residues of parathion were concerned as these were present on the skin of the participants while there was no difference in the dose to which a worker was exposed whether he/she applied mask or not (Spear 2006). c. Explain how researchers could conclude, based on the experimental work in the parathion field studies, that poisonings (such as those listed in Table 2 of “Organophosphate Pesticide Residue Poisoning Among California Farmworkers”) were the result of occupational exposure rather than exposure that may have occurred at home, off-field, etc.? [Hint: The reading “Worker Poisonings Due to Paraoxon Residues” may prove helpful.] Clinical response of humans to exposure to OP compounds is dose related. As there is more concentration of parathion at the work place as compared to office or home and it is present in all its forms (liquid, vapors, concentrated) therefore, the effect of exposure is also maximum when the worker is at the work place as compared to home or office; the effect is further increased because of regular visits to the work place (Spear 2006). 3. In your own words, define cohort, case-control, and cross-sectional study designs. For each design, briefly describe one major advantage and one major disadvantage. Each advantage and each disadvantage should be described in no more than 2 sentences. Cohort study: This is an epidemiological study in which one group of individuals is exposed to a certain condition (exposure) and another group is not exposed and these both groups are followed up for a fixed period of time. Then outcome measures are estimated and compared between the two groups usually in the form of odds ratio (OR). In this type of study exposure is known and the investigator wants to look for its effects and establish a cause-effect relationship (Baker 1999, pp1-40, 143-180) (Bates 2006) (Grein 2003). Advantage: This study design is helpful in establishing a cause-effect relationship between an exposure and an outcome. Disadvantage: Very long period of time is required for the completion of this study during which investigator may lose some of its participants. Case control study: An epidemiological study in which characteristics of a group of individuals (cases) with a certain condition (disease) are compared with characteristics of a group of individuals (controls) who do not have that condition (disease) to look for the association between characteristic and disease. This is the study through which risk factors of a disease can be explored (Baker 1999, pp1-40 143-180) (Bates 2006) (Grein 2003).  Advantage: This is suitable for rare disease investigation. Disadvantage: Selection of valid controls for the cases is a difficult task, which is not always achieved. Cross-sectional study: In cross sectional study, certain characteristics of a population and a condition (disease or family planning use) are explored at a particular point in time. There is no importance on the timing or chronological order of exposure or disease occurrence. This study design is utilized to estimate the prevalence of any condition (Baker 1999, pp1-40, 143-180) (Bates 2006) (Grein 2003). Advantage: This is suitable for persistent diseases. Disadvantage: This is not good for investigation of rare diseases or diseases with short duration. 4. a. Name the three main categories of bias that affect epidemiology studies. 1. Confounding 2. Information bias 3. Selection bias b. A case-control study is investigating kidney cancer risk associated with arsenic in Utah. Cases are obtained from the state cancer registry; controls are recruited by a telephone method. Interviews are carried out at subject’s homes, during which time water samples are collected and later analyzed for arsenic content. For one of the three biases identified above in 4.a., give an example for how the bias might influence the results of this study. In this study, selection bias has been introduced because the population base from where controls are selected (telephone method) is different from the population base of cases (state cancer registry). This error may distort the true association between the exposure (arsenic) and outcome (renal cancer) (Baker 1999, pp1-40, 143-180) (Bates 2006) (Grein 2003). c. A cross-sectional study examines childhood asthma risk associated with current dog ownership by mailing a questionnaire (with a stamped and addressed return envelope) to the house of every child who attends a particular school in a town. The questionnaire does not enquire about other types of animals in the household. For one (different from the one you used in 4.b.) of the three biases identified above in 4.a., give an example for how the bias might influence the results of this study. Information bias has been introduced in this cross sectional study, by posing questions, which are deficient in obtaining appropriate and necessary information for other animals. This bias may distort the results in any direction i.e; overestimation, underestimation or no effect (null effect). In the situation where exposure and outcome are dichotomous as is the case here, information bias moves towards null and concludes that there is no association between the exposure and the outcome, which in reality is there. (Baker 1999, pp1-40, 143-180) (Bates 2006) (Grein 2003). 5. You are asked to conduct a health risk assessment for automotive technicians who are using a solvent for cleaning brakes. A physician has reported that the neurological damage experienced by one of her patients, who is a mechanic, may have been caused by his use of the solvent. List five key questions you will need to answer to perform the risk assessment. 1. Look for the hazard. 2. Decide who can be harmed and how. 3. Evaluate the risk and decide whether the existing precautions are adequate or whether more should be done. 4. Record the findings. 5. Review the assessment and revise it if necessary. (Understanding Risk Analysis 1998) (Five steps to Risk Assessment. 2003) I just want to be clear on this; on pages 9 and 19 in the article “Understanding RISK Analysis” is what you have listed the same as what is written in these pages in reference to the question? (i.e. Source assessment (hazard identification), Dose-response assessment, Exposure assessment, Effects assessment, Risk characterization, etc) Actually what I could gather from various sources, these are five steps should be taken for risk assessment. I did not find better way other than this to present. If you have got some idea please mention I will try to modify it accordingly. 6. a. Write a simple equation that describes the relationship between risk, hazard and exposure. Risk = (Hazard) (Exposure) b. Briefly define and contrast the terms “hazard” and “exposure” as they are used in the assessment of the health risks of chemicals. **Information **Hazard **Exposure Define Anything that can cause harm (i.e. chemicals, electricity) Some one subjected to some situation. Description So hazard is a measurement, which is measured in ratio. Damage caused by a hazard is directly proportional to the dose of an exposure which itself depends on the duration of exposure. Risk Assessment Hazard identification is the first step To update the assessment level, collection of new information/data needed Exposure to the identified hazard is an integral part of assessment which follows identification Other sources of exposure as are identified. Even some assumptions are made if required **Source: (Understanding Risk Analysis 1998) (FDA 2002) 7. Information on a chemical’s toxicity and ecotoxicity can be illustrated using a continuum of theoretical standards of evidence of harm, from scientific suspicion of risk to clear evidence of cause-and-effect: Scientific suspicion Reasonable grounds Balance of Clear evidence of of risk for concern evidence cause-and-effect Each level could arguably be used as the basis for chemical policy decision-making. Using the example of toxic metals (e.g. lead, cadmium and mercury) used in the manufacture of electronic products, describe an advantage and a disadvantage of regulating metals on the basis of clear evidence of cause and effect, and an advantage and a disadvantage of regulating on the basis of scientific suspicion of risk. Each advantage and each disadvantage should be described in no more than two sentences. Clear evidence of cause and effect: There is an established evidence that certain chemicals like mercury and lead at low doses are associated with disruption in the development of brain and nervous system. If regulatory steps are taken to control the use of these chemicals by the industry then there would be a remarkable improvement in the proper development of brain in neonates in the surrounding areas where these chemicals are present in the environment. The disadvantage would be to the industry, which uses these chemicals as administration and production departments’ efficiency may be compromised. Administration will have to take further steps for disposing off the wastes. Scientific suspicion of risk: Fluorinated compounds, perfluorooctane sulphonate (PFOS) have been used as consumer products for “non-stick” and water-repellent properties. There is evidence that it is present in human tissues and in the tissues of birds, fish and marine mammals around the world. But its adverse effects have not been observed. If some regulatory steps are taken then the advantage to the public would be that they will remain protected from its adverse effects if they ever appear. As there would be restrictions on the industry for its concentration used in the products or disposal measures taken which would affect the current level of work, business, staffing and marketing of the industry so may change the performance level of the industry (Understanding Risk Analysis 1998) (Five steps to Risk Assessment. 2003)(Wilson Part I. 2006) (Wilson 2006) (Wilson ppt.) Works Cited Baker D, Kjellstrom T, Calderon R, Pastides H. Environmental Epidemiology: A textbook on Study Methods and Public Health Applications. Ch. 1&2 pp.1-40, 143-180 Prelim Edt. 1999, WHO. Bates M, Introduction to Environmental Epidemiology: Study Designs and Interpretation. ppt, 23 February 2006. Divisional of Environmental Health Sciences, School of Public Health, UC Berkeley. Five steps to Risk Assessment. July 2003. HSE Government of the UK. 06 March 2006. Grein T, Epiet: Bias, ppt. 2003 Health, University of California, Berkeley. Ibrahim M, Alexander L, Shy C, Farr S, Horner R, “ERIC Notebook.” December 1999. University of North California Chapel Hill, School of Public Health, Department of Veterans Affairs, Epidemiologic Research and Information Center, Durham,NC. 04 March 2006. Spear R. Organophosphorus Pesticide Residue Poisoning Among California Farmworkers. 03 June 2006. Understanding Risk Analysis. A short guide for Health, Safety, and Environmental Policy Making, Internet Edt. 1998, American Chemical Society. U.S. Food & Safety Administration Part-I: Overview of CFSAN Risk Analysis Framewrok. March 2002. Center for Food Supply and Applied Nutrition. 09 March 2006 Wilson M, Part I. Do we need a new approach to risk assessment? The 25-year record of the U.S. Toxic Substances Control Act says…“Yes!” 2006. Public Health, University of California, Berkeley. Wilson M, Part II. Some public and environmental health issues pertinent to a discussion of risk assessment. 2006. Public Health, University of California, Berkeley. Wilson M. Risk Assessment, ppt. The Center for Occupational and Environmental Read More