Health issues human exposure

Arsenic in aquatic environments is usually more concentrated in sediments and pore water than in the overlying water column (Ahmann et al., 1997 Smedley and Kinniburgh, 2002 Williams, 2001). The most abundant forms of arsenic are arsenate [As(V)] and arsenite [As(III)], but methylated forms can occur in mine-impacted environments (i.e., methylarsenic acid and dimethylarsenic acid) (Smedley and Kinniburgh, 2002) see Chapter 9.02. The principal pathway of arsenic toxicity is through dietary exposure to sediment and suspended particulates by fish, followed by human consumption. Environmental exposure to arsenic is a causal factor in human carcinogenous and other related health issues. Chronic exposure symptoms in humans include hyperkeratosis, hyperpigmentation, skin malignancies, and peripheral arteriosclerosis. Water provides the dominant pathway for arsenic exposure in humans (Williams, 2001). 

The literature on the neurobehavioral effects of oral exposure to lead in animals is extensive. Only those studies considered key to clarifying human health issues will be presented here. High levels of exposure to lead produce encephalopathy in several species, but blood lead data for this effect are generally not available. 

A guideline to protect human health, by limiting exposure to 1,2-diphenylhydrazine in water, has been issued by the federal government. The U.S. Environmental Protection Agency (EPA) has made recommendations to the concentration of 1,2-diphenylhydrazine in natural waters, such as takes and streams. The EPA has developed regulations to limit the release of 1,2-diphenylhydrazine by industries. Any release of 1 pound or more of 1,2-diphenylhydrazine must be reported to EPA. 

More recently, several authors studied the possible association between fish consumption and levels of PFCs in human blood [138], as well as the evaluation of the risk associated with fish consumption [73, 139]. In recognition of the potential for human exposure to PFCs via fish consumption, the Minnesota Department of Health has issued fish consumption advisories for contaminated sections of the Mississippi River (Minnesota Department of Health 2007). This advisory suggests that people limit their intake of fish to no more than one meal a week if PFOS levels in fillet exceed 38 ng/g. 

Centers for Disease Control and Prevention—National Health and Nutrition Examination Surveys (NHANES) National Reports on Human Exposure to Environmental Chemicals Provides continuing assessment of U.S. population s exposure to environmental chemicals using biomonitoring data from NHANES. First National Report on Human Exposure to Environmental Chemicals (First Report) was issued in March 2001. Second Report, released in January 2003, presents biomonitoring exposure data on 116 environmental chemicals for noninstitutionalized, civilian U.S. population in 1999-2000. Third report was released in July 2005 and includes data on 148 chemicals (CDC 2005). 

The National Dioxin Program has extensively surveyed the levels of dioxins in Australian foods, human milk and the natural environment as well as identifying sources. As a result of this the risks to human health and the natural environment are considered to be minimal. Human health risks from exposure to POPs may continue to be an issue, because of increasing concerns about endocrine disruption and also the possible relationship between residues and specific cancers such as breast cancer. 

Human data are preferred for determining the potential health effects of exposure. However, human studies are often limited by ethical issues in collecting data and by their complexity in establishing exposure conditions and associated effects. Consequently, it is important to understand the various human study designs and their strengths and limitations (see chapter 6). 

NTP (1998) Report on the workshop on Scientific issues relevant to the assessment of health effects from exposure to methylmercury . Research Triangle Park, NC, United States Department of Health and Human Services, National Institute of Environmental Health Sciences, National Toxicology Progam (http //ntp.niehs.nih.gov/ index.cfrn objectid=03614B65-BC68-D231-4E915F93AF9A6872 execsumm). 

Component-Based Methods. Component-based approaches (Figure 5.5) are generally used to evaluate human health risks from exposure to a limited number of chemicals as a mixture. Key issues for component-based assessments include similarity in dose-response curves and similar vs. independent toxic modes of action (MOAs) among mixture components. A distinction can be made between 1) assessments using relatively simple additivity methods without the consideration of potential interaction effects, and 2) assessments that include data on toxicological interactions. Both types of assessments are discussed in more detail below. 

Risk assessment is the scientific evaluation of known or potential advCTse health effects resulting from human exposure to food-borne hazards. The remit of any scientific committees should be regularly reviewed to ensure that the risk assessors are able to address the relevant issues raised by the risk managers, and that no issues are being missed. 

Georgopoulos PC, Roy A, Yonone-Lioy MJ, Opiekun RE, and Lioy PJ (2001) Environmental copper Its dynamics and human exposure issues. Journal of Toxicology and Environmental Health B Critical Reviews 4(4) 341-394. 

The potential for unusual health effects of chemical mixtures due to the interaction of chemicals or their metabolites (e.g., metabolites of trichloroethylene and benzene) in or with the biosystem constitutes a real issue in the public health arena. However, toxicity testing to predict effects on humans has traditionally studied one chemical at a time for various reasons convenient to handle, physiochemical properties readily defined, dosage could easily be controlled, biologic fate could easily be measured, and relevant data were often available from human occupational exposures. Chemicals are known to cause disease for example, arsenic and skin cancer, asbestos and lung cancer, lead and decrements of IQ, and hepatitis B predisposes to aflatoxin-induced liver cancer but the link between the extent of human exposure to even well-defined chemical mixtures and disease formation remains relatively unexplored, but of paramount importance to public health. 

On November 18-20, 1998, a workshop on Scientific Issues Relevant to the Assessment of Health Effects from Exposure to Methylmercury was conducted in Raleigh, North Carolina. The workshop was jointly sponsored by the U.S. Department of Health and Human Services (DHHS), the National Institute of Environmental Health Sciences (NIEHS), the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the U.S. Environmental Protection Agency (EPA), the National Oceanic and Atmospheric Administration (NOAA), the Office of Science and Technology Policy (OSTP), the Office of Management and Budget (OMB), and ATSDR. The purpose of this workshop was to discuss and evaluate the major epidemiologic studies that associated methylmercury exposure and the results of an array of developmental measures in children. These studies monitored and evaluated exposed populations in Iraq, the Seychelles Islands, the Faroe Islands, and the Amazon River Basin. A number of animal studies were also considered in support of a human health risk assessment. 

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