Abstract  A Health Hazard Evaluation investigation was conducted by NIOSH at the working hangars (SIC-4582) of the United Airlines Maintenance Base, Burlingame, California. An authorized employee representative requested the investigation for worker exposure to substances used in the stripping, priming and painting of jet aircraft, and other solvents. Since the operation covers up to 1450 employees, it was decided to conduct a medical study on a representative sample of workers and to take environmental measurements during all operations of industrial hygiene significance. The study revealed that during paint stripping employees without respiratory protection are exposed to potentially toxic concentrations of methylene-chloride (75092), a fact also confirmed by the high rate of complaints of occasional eye irritation, throat irritation, and head congestion when in close proximity to the paint stripping operation. Employees in contact with other solvents, including toluene (108883), isopropyl alcohol (67630), methyl-ethyl-ketone, n-butyl acetate, n-butyl-alcohol, ethyl-acetate, cyclohexanone (108941), methyl-isobutyl-ketone (78933), xylene (1330207), cellosolve-acetate, and phenol (108952), are not exposed to toxic levels of these chemical agents. Employees who spray paint aircraft with paint containing hexamethylene-diisocyanate may be exposed to potentially toxic levels of this agent, although this fact could not be conclusively established. Recommendations are made designed to keep employee exposure to these chemical agents to a minimum.

Abstract  The U.S. Environmental Protection Agency (EPA) is today issuing final amended guidelines for assessing the risks for developmental toxicity from exposure to environmental agents. As background information for this guidance, this notice describes the scientific basis for concern about exposure to agents that cause developmental toxicity, outlines the general process for assessing potential risk to humans because of environmental contaminants, summarizes the history of these guidelines, and addresses public and Science Advisory Board comments on the 1989 “Proposed Amendments to the Guidelines for the Health Assessment of Suspect Developmental Toxicants” [54 FR 9386-9403]. These guidelines, which have been renamed “Guidelines for Developmental Toxicity Risk Assessment” (hereafter “Guidelines”), outline principles and methods for evaluating data from animal and human studies, exposure data, and other information to characterize risk to human development, growth, survival, and function because of exposure prior to conception, prenatally, or to infants and children. These Guidelines amend and replace EPA’s 1986 “Guidelines for the Health Assessment of Suspect Developmental Toxicants” [51 FR 34028-34040] by adding new guidance on the relationship between maternal and developmental toxicity, characterization of the health-related database for developmental toxicity risk assessment, use of the reference dose or reference concentration for developmental toxicity (RfDDT or RfCDT), and use of the benchmark dose approach. In addition, the Guidelines were reorganized to combine hazard identification and dose-response evaluation since these are usually done together in assessing risk for human health effects other than cancer.

Abstract  This chapter examines and compares the acute toxicity in mice and dogs of inhibited methylene chloride, methyl chloroform, and a commercially available paint remover. The introduction of halogens into the molecule of hydrocarbons exerts a pronounced effect not only on the physicochemical properties, but also on the biological behavior of these organic compounds. Halogen substitution usually intensifies the pharmacologic as well as toxicologic properties of a given compound. Both methylene chloride and a paint remover decreased the myocardial contractility and output in the anesthetized open-chest dog preparation. Inhalation of various concentrations of paint remover was associated with various myocardial and hemodynamic changes. The inhalation of paint remover caused an initial increase followed by a decrease in myocardial contractility and cardiac output. The oral route of administration showed no discrimination between the toxicity of methylene chloride and the paint remover.

Abstract  We have developed a chemical mechanism describing the tropospheric degradation of chlorine containing very short-lived substances (VSLS). The scheme was included in a global atmospheric model and used to quantify the stratospheric injection of chlorine from anthropogenic VSLS between 2005 and 2013. By constraining the model with surface measurements of chloroform (CHCl3), dichloromethane (CH2Cl2), tetrachloroethene (C2Cl4), trichloroethene (C2HCl3), and 1,2-dichloroethane (CH2ClCH2Cl), we infer a 2013 mml:msubsup mixing ratio of 123 parts per trillion (ppt). Stratospheric injection of source gases dominates this supply, accounting for approximate to 83% of the total. The remainder comes from VSLS-derived organic products, phosgene (COCl2, 7%) and formyl chloride (CHClO, 2%), and also hydrogen chloride (HCl, 8%). Stratospheric increased by approximate to 52% between 2005 and 2013, with a mean growth rate of 3.7pptCl/yr. This increase is due to recent and ongoing growth in anthropogenic CH(2)Cl(2)the most abundant chlorinated VSLS not controlled by the Montreal Protocol.

Abstract  In 1983, the National Academy of Sciences (NAS)/National Research Council (NRC) published its report entitled Risk Assessment in the Federal Government: Managing the Process. In that report, the NRC recommended that Federal regulatory agencies establish ""inference guidelines"" to promote consistency and technical quality in risk assessments and to ensure that the risk assessment process was maintained as a scientific effort separate from risk management. EPA responded to this recommendation by publishing a set of risk assessment guidelines in 1986, including the Guidelines for Carcinogen Risk Assessment (51 FR 33992, September 24, 1986). EPA began revising the 1986 cancer guidelines in light of significant advances in our understanding of the processes of carcinogenesis and the modes of actions of disease at the cellular level. Revising the cancer guidelines is in keeping with EPA's original intent when it issued the first set of final risk assessment guidelines in 1986. The risk assessment guidelines were meant to be dynamic, flexible documents that would evolve to reflect the current state of the science and risk assessment practices. In keeping with this, EPA undertook an effort to revise the cancer guidelines as described below in the History and Chronology section.

Abstract  Evaluation of environmental risks posed by potentially hazardous substances requires achieving a balance between over- and underprotection. i.e., between societal benefits posed by the use of particular substances and their potential risks. Uncertainty (e.g., only laboratory data may be available, field or epidemiological data may be limited and less than clear-cut, etc.) will always exist and is often conservatively dealt with by the use of so-called "safety" or "uncertainty" factors, some of which remain relatively little changed since their origin in 1945. Extrapolations involving safety factors for both aquatic and terrestrial environments include inter-and intraspecies, acute-to-chronic, lowest-to no-observed-effect concentration (NOEC), and laboratory-to-held extrapolation (e.g., extrapolation of laboratory results to the field). To be realistic, such extrapolations need to have a clear relationship with the field effect of concern and to be based on good science. The end result is, in any case, simply an estimate of a field NOEC, not an actual NOEC. Science-based versus policy-driven safety factors, including their uses and limitations, are critically examined in the context of national and international legislation on risk assessment. Key recommendations include providing safety factors as a potential threshold effects range instead of a discrete number and using experimental results rather than defaulting to safety factors to compensate for lack of information. This latter recommendation has the additional value of rendering safety factors predictive rather than simply protective. We also consider the so-called "Precautionary Principle," which originated in 1980 and effectively addresses risk by proposing that the safety factor should be infinitely large.

Abstract  EU chemicals legislation requires the use of all available information for hazard and risk assessment before new tests on vertebrates are proposed or conducted. In this context, extrapolation approaches for avoiding chronic fish testing on the basis of existing data have been explored. Simple linear relationships and interspecies sensitivity ratios between Daphnia and fish were calculated and acute-to-chronic relationships and ratios were calculated for fish, taking into consideration the mode of action. The best fitted relationships for the prediction of chronic fish toxicity are obtained based on acute fish and Daphnia data. Chemicals acting by unspecific reactivity and non-polar narcosis give the strongest acute and chronic Daphnia-to-chronic fish relationship. With acute fish data, strong relationships are obtained for all mode of action. Daphnia was found to be more sensitive than fish to several aniline derivatives and pesticides acting through cholinesterase inhibition, and less sensitive than fish to known endocrine disruptors. Extreme (i.e. <1 or >100) interspecies sensitivity ratios were mainly evident for chemicals acting by polar narcosis and specific reactivity. The safety factor of 100 commonly applied in environmental risk assessment does not seem to be equally protective for each mode of action.

Abstract  The United States Environmental Protection Agency (U.S. EPA), Office of Pollution Prevention and Toxics (OPPT), identified and chose trichloroethylene (TCE) for risk evaluation as part of its Existing Chemicals Management Program under the Toxics Substances Control Act (TSCA). TCE is a volatile organic compound (VOC) that is classified as a human carcinogen.  Its consumption in the U.S. is 255 million pounds (lbs) per year. TCE is widely used in industrial and commercial processes, and also has some limited uses in consumer products. Main Conclusions of this Risk Assessment This risk assessment identifies cancer risk concerns and short‐term and long‐term non‐cancer risks for workers and occupational bystanders at small commercial degreasing facilities and dry cleaning facilities that use TCE‐based solvents and spotting agents, respectively. EPA/OPPT also identifies short‐term non‐cancer risks for consumers and residential bystanders from the use of TCE‐containing solvent degreasers and spray-applied protective coatings.