Use search engine to find Chronic Particulate Matter Exposure and Coronary Heart

Question

Use search engine to find Chronic Particulate Matter Exposure and Coronary Heart Disease in the Nurses’ Health Study (example study in air pollution lecture). Review the study. Answer the following questions. Minimum of 500 words overall response. What was the study population (detailed overview)? What were the results of the study (Detailed overview)? What was the exposure assessment approach? Strengths? Gaps or weaknesses? What would you do to improve the exposure assessment? What was the epidemiologic study design? Strengths? Gaps or weaknesses? What would you do to improve the epidemiologic study design? Why?

Explanation / Answer

1. The study pollution is Particle Air Pollution.

Coarse particulate matter air pollution and hospital admissions for cardiovascular and respiratory diseases among Medicare patients. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution.

Particle pollution, also called particulate matter or PM, is a mixture of solids and liquid droplets floating in the air. Some particles are released directly from a specific source, while others form in complicated chemical reactions in the atmosphere.

Particles come in a wide range of sizes. Particles less than or equal to 10 micrometers in diameter are so small that they can get into the lungs, potentially causing serious health problems.

2. In general term for extremely small particles and liquid droplets in the atmosphere • PM2.5 (fine particles): d 2.5 m • PM10 (coarse particles): d 10 m

• Primary sources: – Incomplete combustion – Automobile emissions – Dust – Cooking

• Secondary sources: – Chemical reactions in the atmosphere.

3.

Wood-Burning Stoves

Forest Fires

Diesel Engines

Natural Sources

Non-Road Vehicles

Agricultural Burning

Industry

Cars and Buses

Why Is it Important to Communicate Information about Particle Pollution to the Public?

• Exposure to particle pollution is a public health hazard

• When inhaled, particle pollution can travel deep into the lungs and cause or aggravate heart and lung diseases

• Exposure to particle pollution causes increases in:

– Doctor and emergency room visits

– Hospital admissions

– Use of prescription medication

– Absences from work and school

What is the identity and nature of the airborne contaminant?

Specific characteristics of the airborne hazard must be established in order to select an appropriate respirator.

How much employee exposure is there in the workplace?

The final rule permits employers to use many approaches for estimating worker exposures to respiratory hazards.

Variation - You should account for potential variation in exposure by using exposure data collected with a strategy that recognizes exposure variability, or by using worst-case assumptions and estimation techniques to evaluate the highest foreseeable employee exposure levels. The use of safety factors may be necessary to account for uneven dispersion of the contaminant in the air and the proximity of the worker to the emission source.

The Health and Environmental Research Online is a database of scientific studies and other references used to develop EPA's risk assessments aimed at understanding the health and environmental effects of pollutants and chemicals. It is developed and managed in EPA's Office of Research and Development (ORD) by the National Center for Environmental Assessment (NCEA).

Exposure assessment is important in all environmental-epidemiologic studies. A wide range of exposure-assessment strategies and techniques are available for use in environmental-epidemiologic investigation. Associations have been clarified by improved use of exposure assessment even where indirect methods have been used.

Both direct measures (personal and biologic monitoring and biomarkers) and indirect measures (microenvironmental monitoring, diaries, and mathematical modeling) can be used for exposure assessment in environmental epidemiology. Each of these techniques has advantages and disadvantages. Their optimal use depends on the nature of the study, the biologic hypothesis, and resource constraints. No approach should be singled out as being the only acceptable strategy, e.g., personal monitoring. All approaches have validity and will improve the study if used appropriately.

Better exposure assessment in environmental epidemiology will increase the power of studies to find associations. However, within a fixed budget, spending more money on exposure assessment per subject will reduce the number of subjects who can be studied and hence could reduce statistical power. The tradeoff between precision and the cost of larger samples means that power will not increase monotonically with improvements in the accuracy of the exposure assessment. In studies of multifactorial outcomes and low relative risks, a large sample is almost always required. This means that inexpensive methods for modest improvement of rough and inexpensive exposure assessment may be more valuable than more-accurate but expensive methods. This includes very inexpensive methods, such as the use of questionnaire data on activity patterns.

Studies of large populations exposed to mixtures of air pollutants should incorporate detailed estimates of exposure, including detailed activity logs (including transit to work or school), the kind of air conditioning in the home and workplace, and the use of personal monitors to validate models in subsets of the population under study.

The problems of exposure measurement in persons living close to hazardous-waste sites were discussed in volume 1. Most studies have been structured around an "exposed-unexposed" classification or have used surrogates of exposure, such as distance from the waste site. Estimation of past exposures is particularly difficult and unreliable. Misclassification is likely to be a crucial problem in studies of this nature, and improved characterization of exposure is a priority.

The estimation of cumulative doses is an important component of many occupational-exposure studies, though such measures may not be valid even in occupational settings. The exposure-dose relation should be examined for nonlinearity before cumulative estimates are calculated. The relation between cumulative exposure and peak exposure is unknown in many environmental-epidemiologic studies, particularly those involving hazardous-waste site exposures or community exposures to episodic pollution.

The characterization of complex mixtures is a continuing problem for exposure assessment. Four priorities in addressing complex mixtures are quantification of exposure to complex mixtures, characterization of combined or interactive effects, toxicologic characterization of the complex mixture in question, and identification of subpopulations that may be especially sensitive to one or more of the components of certain complex mixtures.

Biologic markers of exposure can strengthen environmental-epidemiologic studies. Unfortunately, few such markers are yet feasible in field studies, and few have been adequately validated. Efforts to improve and refine such indicators are important. The feasibility and value of banking blood samples for future analysis should be considered as studies are designed. Biomarkers of changes induced in the immune system of human subjects are needed.

Health effects are often subtle, and risks are difficult to estimate. As a result, more attention is being given to the estimation of target-tissue dose in ways that reduce misclassification and improve precision. Development of mathematical models to estimate target-tissue dose (toxicokinetic modeling) that may be combined with epidemiologic models to estimate risk is a new and important area of research.

Emphasis should be given to the development of training programs in environmental-exposure assessment. Improvement in the development and use of new techniques in exposure assessment is a high priority in environmental epidemiology.

Data should of course be generated and collected under rigorous conditions of quality control. Bias must be minimized, and variance must be both minimized and estimated when quantitative conclusions are to be drawn. Measures of and checks on data quality should be prominent in every manuscript and report, and authors must not be reticent in bringing out the mechanisms of their study—and there will always be weaknesses. Because of the difficulties of conducting epidemiologic studies, both descriptive and analytic, it is rare for any one study to be definitive, and this is especially true in environmental epidemiology. Every public presentation, written or oral, including reports to scientific colleagues, should contain prominent caveats about overinterpretation.

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