Human health effects, of chemical

Health IfEa (1999) Risk assessment approaches used by UK government for evaluating Human Health Effects of Chemicals. Risk Assessment, Toxicology Steering Committee (RATSC)... 

The institutional fragmentation of chemical mutagenesis also helps explain why concern about the human health effects of chemical pollution arose so late among geneticists—those people almost uniquely situated to understand both the magnitude and the depth of the problem. These institutional constraints and opportunities are the subjects of the next chapter. 

Carpenter DO, Arcaro K, Spink DC. (2002) Understanding the human health effects of chemical mixtures. Environ Health Perspect 110(Suppl l) 25-42. 

Background to Selected Environmental and Human Health Effects of Chemical Warfare Agents... 

A difficulty that should not be overlooked is that airborne particulates are rarely homogeneous. They vary greatly in size and shape, and their chemical composition is determined by factors specific to the source and location of the emissions. The combined effects and interactions of various substances mixed with particulates have not yet been established (except for sulfur dioxide), but they are believed to be significant, especially where long-term exposure occurs. Measurement techniques and their reliability may vary across regions and countries, and so may other factors, such as diet, lifestyle, and physical fitness, that influence the human health effects of exposure to particulates. 

Little is known about the human health effects of diisopropyl methylphosphonate. Skin rashes and other signs of irritation have been reported in some people who handled dead animals near a pond containing diisopropyl methylphosphonate and other chemicals, but it is not known which substances caused these effects. 

Workshop participants suggested that additional research should be conducted on the human health effects of POPs and that systems be established to promote the standardization of toxicity measurement of chemicals and to assess the qualifications of laboratories for toxicity appraisal. Furthermore, Good Laboratory Practice (GLP) laboratories need to be popularized in China to improve the quality and reliability of monitored data. 

Global concerns have been raised in recent years over the potential adverse effects that may result from exposure to chemicals that have the potential to interfere with the endocrine system. WUdlife and human health effects of endocrine dismpting chemicals (EDCs) were first proclaimed by Rachel Carson in 1962, and based on a growing body of knowledge those concerns have increased. This concern regarding EDCs is directed at both humans and wildlife (WHO/IPCS 2002). 

This section outlines the current scientific state of the art in the assessment of human health risks for chemical mixtures. It focuses on the gathering, assessment, and evaluation of effect data. The reader is referred to Chapter 1 for detailed information on exposure assessment of chemical mixtures. The section starts with an overview of methods commonly used to obtain effect data on chemical mixtures. This is followed by an overview of the current mixture approaches in human health assessments, that is, the whole mixture approach for common mixtures and the component-based approach. The section concludes with a paragraph on uncertainties in human health assessments of chemical mixtures. 

Risk assessment of potential adverse human health effects from chemical mixture exposures may be conducted using health effects information from 1) toxicological bioassays, 2) epidemiological studies, and 3) computer models of toxicokinetic and toxicodynamic processes (i.e., in silico toxicology). 

Chronic toxicity studies provide information on the long-term health effects of chemical substances. Adverse health effects in exposed animals and subsequent severe damage are known to occur after repeated exposure to low doses over a period of time. The slow accumulation of mercury or lead in the body or after a long latency period from exposure to chemical carcinogens is an example. Chronic or prolonged periods of exposure to chemical substances may also cause adverse effects on the reproduction and behavior of animals and humans. The symptoms caused after chronic exposure usually differ from those observed in acute poisoning from the same chemical. In fact, when exposed to low concentrations of chemical substances, as is the case with chronic toxicity studies, the industrial worker and common public are unaware of the exposure. 

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. 

Faroon O, Kueberuwa S, Smith L, and DeRosa C (1995) ATSDR evaluation of health effects of chemicals. II. Mirex and chlordecone Health effects, toxicokinetics, human exposure, and environmental fate. Toxicology and Industrial Health 11(6) 1-203. 

Matthews EJ, KruhlakNL, Benz RD, Contrera JF. Assessment of the health effects of chemicals in humans I. QSAR estimation of the maximumrecommended therapeutic dose (MRTD) and no effect level (NOEL) of organic chemicals based on clinical trial data. Curr Drug Discov Technol 2004 Jan l(l) 61-76. 

The EPA had concerns similar to those of the FDA. Under section 4 of the Toxic Substances Control Act (TSCA), the EPA evaluates laboratory data submitted to the agency regarding tests of the health effects of chemical substances and mixtures. Also, under authority of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the EPA evaluates laboratory test data relating to hazards to humans arising from the use of a pesticide product when the agency evaluates pesticide registration applications. 

Nelson, N. (Chairman). 1983. Research Briefing Panel on Human Health Effects of Hazardous Chemical Exposures. Committee on Science, Engineering and Public Policy. National Academy Press, Washington, DC P 100-110. 

Because there is rarely actual data on the mixture of concern, an additivity approach (adding all the toxic effects of the individual components) is sometimes used. This approach involves a number of assumptions and has certain limitations due to the lack of consideration for potential synergism or antagonism between individual chemical compounds. Further research is needed on human health effects from chemical mixtures to more accurately predict the risks involved in these common environmental situations. 

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