Human Populations at Risk

But here too, some basic difficulties can present themselves. For assessing the possibility of cancer — the main objective in long term tests — we rely on the use of healthy, disease-free inbred mice, which represent characteristics that are hardly representative of a heterogeneous human population at risk. This difference only complicates known differences in metabolic responses ... 

Some animal studies indicate that dietary exposure to methyl parathion causes decreased humoral and cellular responses (Shtenberg and Dzhunusova 1968 Street and Sharma 1975). A more recent, well-designed animal study that included a battery of immuno/lymphoreticular end points showed few effects at the nonneurotoxic doses tested (Crittenden et al. 1998). No adequate studies are available in humans to assess the immunotoxic potential of methyl parathion. Therefore, studies measuring specific immunologic parameters in occupationally exposed populations are needed to provide useful information. Further studies are also needed to investigate the mechanism for methyl parathion-induced immunotoxicity since this information would help to identify special populations at risk for such effects. 

Cataldo, A.M., Hamilton, D.J., Barnett, J.L., Paskevich, P.A., and Nixon, R.A., 1996, Properties of the endosomal-lysosomal system in the human central nervous system disturbances mark most neurons in populations at risk to degenerate in Alzheimer s disease. J. Neurosci. 16 186-199... 

If HI is less than one, it may be inferred that even those in the human population at the high end of exposure do not incur doses in excess of the estimated threshold dose, and so are unlikely to be at risk of toxicity. For His that exceed one, it may be inferred that some fraction of the population is at risk of toxicity, and the larger the HI, the larger the (non-quantified) risk. 

Malaria remains one of the most important diseases of humanity with over half of the world population at risk of infection. It affects mainly those living in tropical and subtropical areas with an incidence of 500 million cases per year globally. The antimalarial activity of 4-(5-trifluoromethyl-17/-pyrazol-l-yl)chloroquine analogues 875 has been evaluated in vitro against a chloroquine-resistant Plasmodium falciparum clone <2006BML649>. 

One explanation that has been proposed for the differences in occurrence of human and animal prion diseases is age-distribution. The farm animal population at highest risk for development of sporadic or familial prion disease is the elderly segment, which is normally quite small in production animals. The likelihood of discovery is further reduced by low disease incidence and challenging diagnostics. Thus, large-scale surveillance programs, with particular scrutiny of the populations at risk, have proved vital in the discovery of atypical ruminant prion diseases, as detailed in this chapter. 

Current disposal methods include liquid injection incineration, rotary kiln incineration, fluidized bed incineration, and air stripping (HSDB 1995), however, data on the efficiency of these methods are lacking. This information will be useful in identifying the media of concern for human exposure and populations at risk of adverse health effects from exposure to carbon disulfide. 

Human risk is often considered both in terms of individual risk (which is independent of population density) and societal risk (which depends on the size of the population at risk and therefore considers the population contained in a geographical area). Both individual and societal risk are important when examining the potential for accidental exposures, individual risk is the usual form considered when dealing with anticipatable human exposure. Most non-human environmental risks are considered mainly in terms of effects on populations and communities, ie, in terms similar to human societal risk ... 

By 2000, 68% of the population at risk had been covered by USI, which requires all salt for human and animal consumption to be iodized with potassium iodate at a level of 20—40 mg iodine/kg of salt. 

Water collected from the envirorunent contains trace quantities of dissolved and suspended matter of mineral, plant, and even animal origin, which may create color, taste, and odon It is also very likely to contain a diverse population of mircoorganisms and chemicals that may put human health at risk. The protection of water sources from human or animal pollutants should minimize contamination. 

Part 4 consists of five chapters that provide quantification of the health risks of lead exposure in segments of human populations at significant risk of adverse health effects from such exposures. They sequentially present and quantify risk expressions using a reasonable and generally acceptable model of human health risk assessment for those contaminants such as environmental lead that have already been emitted into the human environment. Such a risk assessment model proceeds through merging and quantitative integration of the previous parts of this book and attempts to answer the question of how much of a threat to human health lead exposures pose. 

Lead would appear to be a particularly valuable, even unique, model for assessing human health risk assessments for toxic environmental contaminants. There are several factors establishing that status. The first is the amount of available data and the nature of that data. Second, we can identify subsets of human populations at particular risk for both exposure to and toxic effects of lead. Third, the available data for Pb and public health readily partition into the typical components of risk assessment. Finally, all data components present with acceptable quality in the nature and extent of the information. 

Human Populations at Higher Risk for Pb exposure and Toxicity... 

To date, the great majority of published and accepted dose—response relationships for lead in various human populations at increased risk have entailed blood lead values for the dose portion. 

While we re not opposed to voluntary measures, we maintain there is no need for them, said Steve Sanetti, president of NSSF. The firearms industry supports science-based decisions about wildlife management. Under current regulations, there is no scientihc evidence showing that the health of wildlife populations and humans is at risk from the use of traditional ammunition. ... 

The Twenty-Fifth Annual Conference on Trace Substances in Environmental Health was held at the University of Missouri, May 20-23, 1991. Findings and recommendations conclude that (1) lead is ubiquitous in the human environment (2) any lead exposure assessment must analyze all potential sources and exposure pathways and (3) acceptable soil lead levels can be determined only through an approach that takes into account numerous factors including but not limited to the population at risk, the physical availability of the lead, and the bioavailability of the lead, which is the amount of lead that can be ingested into the blood stream. 

As described above, the nature of the food supply will provide some information on the likelihood of risk of inadequate dietary zinc within a population. Information compiled by the United Nation s Food and Agriculture Organization has been used to estimate the potential risk of inadequate zinc in the food supply for a large number of countries. This estimate uses country level data on the per capita amounts of 95 different food commodities available for human consumption, and estimates of the zinc content and phy-tate zinc molar ratio of these foods, to calculate the per capita amount of bioavailable zinc in the food supply. The per capita amount of bioavailable zinc is compared to the physiological requirement for absorbed zinc weighted for the demographic distribution of the population. The theoretical proportion of the population at risk of inadequate dietary zinc is used to estimate the relative risk of zinc deficiency at the national level. For example, countries with 25% or more of the population at risk of inadequate dietary zinc are considered to be at elevated risk. This information is limited in that it represents the national average situation and cannot identify subnational populations that may be at elevated risk. In the absence of more direct measures of zinc status, such estimates will justify the need to conduct population surveys that measure risk of zinc deficiency more directly. 

Jacobson-Kram, D. Albertini, R.J. Branda, R.F. Falta, M.T. Lype, R.T. Kolodner, K. Liou, S.-H. McDiarmid, M.A. Morris, M. Nicklas, J.A. ONeill, J.P. Poirier, M.C. Putman, D. Strickland, P.T. Williams, J.R. Xiao, S. 1993. Measurement of Chromosomal Aberrations, Sister Chromatid Exchange, hprt Mutations, and DNA Adducts in Peripheral Lymphocytes of Human Populations at Increased Risk for Cancer. Environmental Health Perspectives Supplements, v.lOl, p.121-125. 

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