Environmental exposures

Chronic Environmental Exposure Itai-itai disease (for details, see Part III, Chapter 6) was first reported in 1955 among the human population of Toyoma, Japan. Urinary cadmium levels were found to be high in affected patients. Studies showed that cadmium content was particularly high in rice, a staple food for this population. The source of cadmium was felt to be via water from the Kamiaha mine upstream from Toyama. It was concluded that cadmium played the most important role in the development of Itai-itai disease (Friberg et al. 1979). 

Minamata disease was first discovered in 1956 around Minamata Bay, Japan. A similar epidemic occurred in 1965 along the Agano river, Japan. Minamata disease is methyl mercury poisoning that occurred in humans who ingested fish contaminated with methylmercury discharged in waste water from a chemical plant. Methylmercury is also teratogenic (Ui 1992, Harada 1995, Eto 1997, Schardein 2000 see also Part III, Chapter 17). 

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Because of the extreme toxicity of this material and the possibiUty it could be present in failed circuit breakers containing decomposed SF, several studies have been carried out to develop analytical methods and investigate possible ways to minimize environmental exposure. One method capable of determining S2F2Q in the ppb range has been reviewed (123). 

Unsaturated resias based on 1,4-cyclohexanedimethanol are useful ia gel coats and ia laminating and molding resias where advantage is taken of the properties of very low water absorption and resistance to boiling water (6). Thermal stabiHty is imparted to molding resias, both thermoplastic (71,72) and thermoset (73—76), enabling retention of physical and electrical properties at elevated temperatures (77). Additionally, resistance to chemical and environmental exposure is characteristic of products made from these resias (78). 

A knowledge of the molecular composition of a petroleum also allows environmentalists to consider the biological impact of environmental exposure. Increasingly, petroleum is being produced in and transported from remote areas of the world to refineries located closer to markets. Although only a minuscule fraction of that oil is released into the environment, the sheer volume involved has the potential for environmental damage. Molecular composition can not only identify the sources of contamination but also aids in understanding the fate and effects of the potentially hazardous components (7). 

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

As part of TSCA, EPA can require the testing of any chemical if there is the possibiUty of an unreasonable risk to health or environment or if there is significant human or environmental exposure. If the substance poses an unreasonable risk, EPA can prohibit the manufacture, processing, or distribution of the substance limit the amount of the substance that can be manufactured, processed, or distributed prohibit a particular use for the substance limit the concentration of the substance during manufacture, processing, or distribution regulate disposal methods for the substance and require manufacturers to maintain records of process and to conduct tests to assure compliance with EPA rules. 

Pharmacokinetic studies should allow an assessment of the relationship between the environmental-exposure conditions and the absorbed dose, and how these influence the doses of test material and metaboHtes received by various body tissues and fluids, and the potential for storage. Numerous texts are available on the design and conduct of metaboHsm and pharmacokinetic studies (117—119). 

L. P. Brown, D. G. Earrar, and C. G. DeRooij, Health Risk Assessment of Environmental Exposure to Trichloroethylene, Regulatory, Toxicol Pharmacol 11, 24-41 (1990). 

Environmental exposures to PCBs are significantly lower than those reported in the workplace and are therefore unlikely to cause adverse human health effects in adults. However, it is apparent from the results of several recent studies on children that there was a correlation between in utero exposure to PCBs, eg, cord blood levels, and developmental deficits (65—68) including reduced bkth weight, neonatal behavior anomaUes, and poorer recognition memories. At four years of age, there was stiU a correlation between prenatal PCB exposure levels and short-term memory function (verbal and quantitative). In these studies the children were all exposed to relatively low environmental levels of PCBs. Although these effects may be related to other contaminants, it is clear that this is an area of concern regarding the potential adverse human health impacts of PCBs. 

Beyond the simple resistance of a material of construction to dissolution in a given chemical, many other properties enter into consideration when makiug an appropriate or optimum MOC selection for a given environmental exposure. These factors include the influence of velocity, impurities or contaminants, pH, stress, crevices, bimetallic couples, levels of nuclear, UV, or IB radiation, microorganisms, temperature heat flux, stray currents, properties associatea with original production of the material and its subsequent fabrication as an item of equipment, as well as other physical ana mechanical properties of the MOC, the Proverbial Siebert Changes in the Phase of the Moon, and so forth. 

There have been suggestions of alterations in sex ratios following accidental environmental exposure to dioxin in Seveso, Italy, in 1976. Between 1977 and 1984, 74 births occurred in the most heavily contaminated zone which showed an excess of females (26 males and 48 females born). Preliminary evidence suggests that the excess was associated with high dioxin exposure in both parents. Over a later period, between 1985 and 1994, the ratio declined (60 males and 64 females) and was no longer statistically significant. 

In exposures by inhalation of airborne materials, the dose is the concentration multiplied by the time (CT), and is roughly a constant for any given material and specified effect. The CT value can be used to provide a rough approximation of other combinations of concentration and time which would have about the same effect. Although this concept must be used very cautiously and cannot be applied at extreme conditions of either concentration or time, it is most important in setting limits for airborne contaminants and physical agents in respect to environmental exposures. The worker is exposed for various periods of time, day after day, to the... 

The harmful effects of industrial emissions are not confined to the workers but extend beyond the plant boundary line. Chemically-induced diseases among workers exposed to industrial chemicals are a warning sign of the risks to which a larger population is also being exposed usually the chemical hazards are in principle similar in the occupational and general environment. However, occasionally environmental exposures can be qualitatively different from the occupational environment and may also cause deleterious health effects in the general population. 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Tsai listed and quantitatively discussed specific degradation mechanisms for environmental exposure [6-40] ... 

All finishes should be selected to be resilient to expected average and worst-case environmental exposure such as high/low humidity or temperature, airborne contaminants, vibration, possible aggressive liquid spillages, cleanliness/hygiene requirements, etc. 

The conditions of environmental exposure play a key role in determining anode performance. Indeed, specific environments often preclude, or necessitate, the use of particular anode materials. 

Standard reference test method for making potentiostatic and potentiodynamic anodic polarisation measurements Recommended practice for atmospheric environmental exposure testing of nonmetal-lic materials... 

Thus, whether the changes in the material are due to chemical reactions, volatilization, or diffusion, one can expect a linear relationship between the logarithm of life (i.e., time to failure) and the reciprocal of absolute temperature. But there is no sound basis for extrapolating the effect of changing the concentration of the environmental exposure medium or the physical functions. 

The next step in the design procedure is to select the materials. The considerations are the physical properties, tensile and compressive strength, impact properties, temperature resistance, differential expansion environmental resistance, stiffness, and the dynamic properties. In this example, the only factor of major concern is the long-term stiffness since this is a statically loaded product with minimum heat and environmental exposure. While some degree of impact strength is desirable to take occasional abuse, it is not really subjected to any significant impacts. 

In terms of environmental exposure, water and humidity must be carefully evaluated in electrical applications. In general, if a plastic absorbs a significant amount of water, the electrical resistivity drops. As examples this is the case for nylons and phenolic. Care must be used in selecting a dielectric to insure that the electrical properties such as the insulation resistance and dielectric strength, as well as other electrical properties are adequate under the conditions of field use, particularly if this involves exposure to high humidity conditions. Temperature also causes changes in most electrical products. 

As most organotins decompose, boiling points of 250 °C were assumed in the absence of a "true boiling point. The values for Henry s law constant and organic carbon/water partition coefficient were all derived from EUSES unless otherwise indicated. The chlorides were chosen as soluble salts in this table toxicity is independent of salt (see section 8), and soluble salts maximize likely environmental exposure, giving worst case in modelling environmental fate. 

BACKGROUND AND ENVIRONMENTAL EXPOSURES TO METHYL PARATHION IN THE UNITED STATES... 

A recent method to screen the urine for alkyl phosphates as an indicator of exposure to organophosphate insecticides shows that the method can be used to determine environmental exposure to a specific organophosphate pesticide. The method was found to be sensitive, identifying low levels of exposure to insecticides in the environment by quantitation of urinary phosphates (Davies and Peterson 1997). The test is limited in that it is only useful for assessing recent exposure, due to the short half-life of the organophosphate pesticides. 

Risk Factor—An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or inherited characteristic, that is associated with an increased occurrence of disease or other health-related event or condition. 

Case Studies in Environmental Medicine Taking an Exposure History—The importance of taking an exposure history and how to conduct one are described, and an example of a thorough exposure history is provided. Other case studies of interest include Reproductive and Developmental Hazards Skin Lesions and Environmental Exposures Cholinesterase-Inhibiting Pesticide Toxicity and numerous chemical-specific case studies. 

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