Occupational Respiratory Disease
Number of Deaths
In this report, the number of deaths for each occupational respiratory condition is the number of decedents for which the condition was coded as either an underlying or contributing cause of death. For the years 1968–1998, these numbers were tabulated from the record axis of the National Center for Health Statistics (NCHS) multiple-cause-of-death data files. Beginning with the 1999 data, these numbers were tabulated from the entity axis and the underlying cause of death of the multiple-cause-of-death data files. A small number of deaths in 1999 with underlying cause code J65 (pneumoconiosis associated with tuberculosis) were included in tabulations of the underlying cause of death for each type of pneumoconiosis. Similarly, deaths in 1999 with underlying cause code J92.0 (pleural plaque with asbestos) were included in tabulations with asbestosis as the underlying cause of death. The number of deaths by condition is reported both annually and for selected time periods. Reported deaths are restricted to U.S. residents aged 15 or older based on State of residence at death. Race was classified as white, black, and all others.
Industry and Occupation Codes and Titles
Since 1993, the 1990 U.S. Census Bureau occupation and industry titles and three-digit codes [Census 1992] have been used for coding death certificate information in the NCHS multiple-cause-of-death data files (see Technical Appendix for 1995 at www.cdc.gov/nchs/about/major/dvs/mcd/1998mcd.htm). Occupation and industry mortality data for 1984–1992 were based on the 1980 Census Bureau occupation and industry classifications [Census 1982]. Most codes and titles in the 1990 system do not differ from the 1980 system. The primary industries associated with silicosis and work-related asthma cases in the SENSOR sections of this report are grouped by the 1987 SIC system. However, the primary occupations are grouped by the 1990 Census Bureau classification system.
Age-Adjusted Mortality Rates
Age-adjusted mortality rates presented in this report were based on deaths with the condition of interest mentioned as an underlying or contributing cause of death. Rates were calculated annually for each specified condition from 1968 through 1999, as well as for selected periods. For a given year, the age-adjusted rates represent the rates that would have been observed if the age-specific rates for specified age groups had occurred in a population with the same age distribution as the standard population. To conform with current NCHS guidelines, the year 2000 standard population [Anderson and Rosenberg 1998] was used as the standard. The age intervals used were 15–24, 25–34, 35–44, 45–54, 55–64, 65–74, 75–84, and 85 years and older. Rates for the entire U.S. population and for each sex-race group were age-adjusted separately, using the same standard population.
Age-adjusted rates were computed by the direct method. First, the annual age-specific rates for the population were calculated. The product of the age-specific rates and the number in the comparable age-specific group in the standard population equals the expected number of deaths per million population for each age group. The total expected numbers of deaths were then obtained by adding all age groups. The total expected number of deaths was divided by the sum of the standard population and the resulting quotient was multiplied by 1,000,000 to produce the age-adjusted rate (per million).
Age-adjusted rates were computed at the national and State level for the period 1990–1999. Rates also were computed at the county level either for two 15-year periods and one 30-year period (1970–1984, 1985–1999, and 1970–1999) or for a single 20-year period (1980–1999), depending on whether the condition was discretely classified during those time periods. Rates for malignant mesothelioma were computed for 1999 only. For each time period (1970–1984, 1970–1999, 1980–1999, 1985–1999, and 1990–1999), age-specific rates were first computed by dividing the average annual number of deaths in each age group by the corresponding age-grouped, mid-year population (1977, 1985, 1990, 1992, and 1995, respectively) in the comparable geopolitical unit. Age-adjusted rates then were computed as described above.
Proportionate Mortality Ratio (PMR)
The data used for PMR analyses are a subset of the NCHS multiple-cause-of-death files for which usual industry and occupation codes are available and meet quality criteria set by NCHS. The PMR is defined as the observed number of deaths with the condition of interest (mentioned as either underlying or contributing) in an industry/occupation from selected States and years, divided by the expected number of deaths with that condition. The expected number of deaths is the total number of deaths in the industry or occupation classification of interest multiplied by a proportion. This proportion is defined as the number of cause-specific deaths for the condition of interest in all industries/occupations divided by the total number of deaths in all industries/occupations. The PMRs in this report have been internally adjusted by 5-year age groups (i.e., 15–19, 20–24, …, 110–114, and 115 years and over), sex, and race (i.e., white, black, and all other). Confidence intervals were calculated assuming Poisson distribution of the data.
A PMR greater than 1.0 indicates that more deaths were associated with the condition in an occupation or industry than expected. This report includes only those industries/occupations with 5 or more decedents with the condition and a lower 95% confidence limit exceeding 1.0.
For further information, contact
Public Health Surveillance Team
Surveillance Branch
Division of Respiratory Disease Studies
National Institute for Occupational Safety and Health
1095 Willowdale Road
Morgantown, WV 26505–2888
Telephone: 304–285–6115
