Public health factors

The remainder of this chapter discusses the evidence for the various causal relationships between Pb exposure and toxicity and disease. As set forth in Table 21.2, adverse human health effects of lead are placed in causal context using the nine proofs-of-causality criteria first enunciated by British medical statistician Sir Austin Bradford Hill in 1965 and subsequently labeled Hill s Criteria of Causation. These criteria are relevant and of particular value in the environmental epidemiology of Pb, given the many contentious arguments over association versus cause that have been lodged against Pb s human health impacts, particularly in earlier eras of lead health research and in the evolution of Pb as a major public health factor. 

On-Site Storage Factors that must be considered in the on-site storage of solid wastes include (1) the type of container to be used, (2) the container location, (3) public health and aesthetics, (4) the collection methods to be used, and (5) future transport method. 

Epidemiology operates within the context of public health with a strong emphasis on the prevention of disease through the reduction of factors that may increase the likelihood that an individual or group will suffer a given disease. Implicit in the practice of epidemiology is the need for different disciplines in studying the influence of occupation on human health. 

The varying metabolic activities of bacteria and their response to immediate environmental factors have been exploited in the design of special diagnostic and selective media. Recipes for these run into many hundreds such media are used in hospital and public health laboratories for identifying organisms found in samples believed to be contaminated by them, and as an aid to diagnosis and treatment. In addition they are used to detect contaminants in pharmaceutical products (British Pharmacopoeia 1993). A few examples will be given to illustrate the principle. 

Tikkanen J, Heinonen OP. 1991. Risk factors for ventricular septal defect in Finland. Public Health 105 99-112. 

C. J. L. Murray and A. D. Lopez, eds., The Global Burden of Disease A Comprehensive Assessment of Mortality and Disability from Diseases, Injuries, and Risk Factors in 1990 and Projected to 2020, Harvard School of Public Health, World Health Organization, and World Bank, Boston 1996. 

Blood was studied in a group of virtually healthy adolescents aged 14-17 from two localities in the Ukraine, where pesticide exposure differed by a factor of three, though the pesticide content in food products, drinking water, air and soil in the experimental zone was not higher than public health standards permitted. In Azerbaijan there was a difference of 100 times in the amounts of pesticides used in the experimental and control localities, while the pesticide contamination of elements of the environment and food products in the experimental zone was 2-50 times higher than acceptable levels [A97]. Table 3.6 shows the results. 

To help prevent this, the U. S. Public Health Service has recommended a maximum limit of 0.5 ppm mercury in any food. If the fish are to have less than this level of methyl mercury and the concentration factor is 3,000, then the surrounding water in which the fish live should have less than 0.16 ppb (parts per billion). Currently the oceans have about 0.1 ppb, but it is not known whether this is in the form of organic or inorganic compounds.8 It is also not known whether fish can convert inorganic mercury into methyl mercury.8 However, a large number of microorganisms can do this, so possibly its usual form is unimportant. 

PEL Pg pmol PHS PMR ppb ppm ppt REL RfD RTECS sec SCE SIC SIR SMR STEL STORET TLV TSCA TRI TRS TWA u.s. UF yr WHO wk permissible exposure limit picogram picomole Public Health Service proportionate mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances second sister chromatid exchange Standard Industrial Classification Standardized incidence ratio standard mortality ratio short term exposure limit STORAGE and RETRIEVAL threshold limit value Toxic Substances Control Act Toxics Release Inventory total reduced sulfur time-weighted average United States uncertainty factor year World Health Organization week... 

It should be noted that the effects of blood lead on IQ and other neurobehavioral scores are very small compared with the effects of other factors such as parent s IQ or vocabulary (Fulton et al. 1987 Pocock et al. 1987 Winneke et al. 1985a). Lead neurotoxicity, however, may have major implications for public health when exposure is considered in terms of large populations and its preventable nature (Davis and Svendsgaard 1987 Grant and Davis 1989). 

Haglund B, Cnattingius S. 1990. Cigarette smoking as a risk factor for sudden infant death syndrome A population-based study. Am J Public Health 80 29-32. 

Mielke HW, Anderson JC, Berry KJ, et al. 1983. Lead concentrations in inner-city soils as a factor in the child lead problem. Am J Public Health, 73 1366-1369. 

The objectives of this study are to determine the frequency distribution of radon levels in residential structures on a nationwide basis and to investigate factors which affect these levels. This study is needed to obtain a more accurate estimate of the average radon level in homes and to provide reliable data on the number of homes exceeding various radon levels. Such information will provide a better understanding of the magnitude of the public health problem associated with indoor radon levels. In addition this information will establish the base line level against which results of other surveys and indoor radon measurements can be compared. 

All of these chemicals pose an inhalation hazard but a toxic dose could also be obtained through skin absorption or ingestion. Factors that were considered when selecting potential candidate chemicals include global production, physical state of the material (i.e., gas, liquid, or solid), chemicals likely to cause major morbidity or mortality, potential to cause public panic and social disruption, chemicals that require special action for public health preparedness, history of previous use by the military, and/or involvement in a significant industrial accident. 

More recently, standard tuberculosis has become a common infection in AIDS patients. TB was largely eradicated in Western countries through public health measures and antibiotic treatments. However, recently there has been a resurgence of TB, due to a combination of several factors (1) immigration from areas where TB infection is still common (Asia and Latin America) (2) decline in public health funding and (3) AIDS patients, who are highly susceptible to TB infection and who in turn can transmit the bacterium. 

Without appropriate cleanup measures, BTEX often persist in subsurface environments, endangering groundwater resources and public health. Bioremediation, in conjunction with free product recovery, is one of the most cost-effective approaches to clean up BTEX-contaminated sites [326]. However, while all BTEX compounds are biodegradable, there are several factors that can limit the success of BTEX bioremediation, such as pollutant concentration, active biomass concentration, temperature, pH, presence of other substrates or toxicants, availability of nutrients and electron acceptors, mass transfer limitations, and microbial adaptation. These factors have been recognized in various attempts to optimize clean-up operations. Yet, limited attention has been given to the exploitation of favorable substrate interactions to enhance in situ BTEX biodegradation. 

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