Impact can be assessed for individuals and small populations or whole systems. The analyst usually uses the following steps to determine the impact on human health and safety: (1) hazard identification, (2) risk assessment, (3) exposure assessment, and (4) risk characterization. (See Section 11.8.)
Determining health risks from many design activities can be difficult. Experts, including toxicologists, industrial hygienists, and physicians, should be consulted in this process. Data sources for health risk assessment include biological monitoring reports, epidemiological studies, and bioassays. Morbidity and mortality data are available from sources such as the National Institute of Health, the Center for Disease Control, and the National Institute of Occupational Safety and Health.
The following ways are available to assess health impact: the threshold limited value-time-weighted average (TLV-TWA), the medium lethal dose (LD), the medium lethal concentration (LC), the no observed effect level (NOEL), and the no observed adverse effect level (NOAEL). (See Section 11.8.)
Other methods are used to compare the health impact of residuals. One approach divides emissions by regulatory standards to arrive at a simple index (Assies 1991). This normalized value can be added and compared when the emission standard for each pollutant is based on the same level of risk. However, this situation is rare. In addition, such an index reveals neither the severity nor whether the effects are acute or chronic. Properly assessing the impact of various releases on human health usually requires more sophistication than a simple index.
Impact on humans also includes safety. Unsafe activities cause particular types of health problems. Safety usually refers to physical injury caused by a chemical or mechanical force. Sources of safety-related accidents include malfunctioning equipment or products, explosions, fires, and spills. Safety statistics are compiled on incidences of accidents, including hours of lost work and types of injuries. Accident data are available from industry and insurance companies.
Health and safety risks to workers or users also depend on ergonomic factors. For tools and similar products, bio-mechanical features, such as grip, weight, and field of movement influence user safety and health.
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