Work-Related Lung Disease (WoRLD) Surveillance System

MORTALITY

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 an entity axis multiple cause-of-death by NCHS. (Note: The WoRLD Surveillance Report 2002 included the number of decedents for the record axis multiple cause-of-death for years 1968-1998 and the entity axis multiple cause-of-death for 1999. Changing to the entity axis multiple cause-of-death permits more complete ascertainment of the diseases of interest.)

Since 1999, deaths with underlying cause ICD-10 code J65 (pneumoconiosis associated with tuberculosis) are included in the underlying cause-of-death tabulations of each specific type of pneumoconiosis (except byssinosis). Similarly, deaths with underlying cause code J92.0 (pleural plaque with presence of asbestos) are included in asbestosis underlying cause-of-death tabulations. Cause-of-death codes are defined as shown in Appendix C: International Classification of Diseases (ICD) Codes. The number of deaths by condition are reported both annually and for selected time periods. Reported deaths are restricted to United States residents, 15 years or older, based on state of residence at death. Race is classified as white, black, and all others.

See "Detail Record Layout"at www.cdc.gov/nchs/about/major/dvs/mcd/1998mcd.htm for a discussion of the appropriate uses, advantages, and disadvantages of the multiple cause-of-death code fields (entity axis and record axis).

Crude Mortality Rates
To compute annual cause-specific crude mortality rates, the total number of decedents, 15 years and older, with a specified condition coded as either underlying or contributing cause in a given year was divided by the population, 15 years and older, of the same geopolitical unit in the same year. Race- and sex-specific rates were computed from the appropriate subsets of the data. Crude mortality rates were computed at the national and state level for the multi-year period 1990-1999, and at the county level for the multi-year period 1985-1999. For each time period, the average annual number of decedents, 15 years and older, with a specified condition coded as either underlying or contributing cause was divided by the mid-year population (1995, 1992, respectively), 15 years and older, of the same geopolitical unit.

Age-Adjusted Mortality Rates
Age-adjusted mortality rates presented in this report were based on deaths with the condition of interest mentioned as either 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 that of the standard population. To conform with current NCHS guidelines, the U.S. Year 2000 Standard Population was used as the standard. (All earlier editions of the Work-Related Lung Disease Surveillance Report have used the 1940 standard population.) The specific 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 United States 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 of interest 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 summing over 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 multi-year 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 or not the condition of interest was discretely classified during those time periods (see Appendix C). 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 first were 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.

Years of Potential Life Lost (YPLL)
YPLL were based on deaths with the condition of interest mentioned as either underlying or contributing cause of death. They were calculated using the method described by the Centers for Disease Control (CDC) (MMWR December 19, 1986/35(2S);1s-11s at www.cdc.gov/mmwr/preview/mmwrhtml/00001773.htm). YPLL were calculated both to age 65 and to life expectancy. YPLL to age 65 may be considered as a loss of years from a traditional working life, while YPLL to life expectancy may be considered as a loss of years from the overall life span. To compute YPLL to life expectancy, the number of deaths in each race/sex age group (the same age intervals used for computing age-adjusted rates) first was multiplied by the difference between the mid-point of the age group and life-expectancy for that race/sex age-group. Life tables published annually by NCHS (www.cdc.gov/nchs/products/pubs/pubd/lftbls/life/1966.htm) were used to determine race/sex life-expectancies for white/male, white/female, black/male, and black/female. The overall U.S. population life-expectancy was used for other/male and other/female. To compute YPLL to age 65, the number of deaths in age groups 15-24 through 55-64 was multiplied by the difference between 65 years and the mid-point of each age group (e.g., 65 minus 20 years for the 15-24 age group). These age-specific YPLLs then were summed over all age groups to obtain total YPLLs (to life expectancy, and to age 65) for each race/sex/year from 1990 to 1999.

State-specific YPLLs (to life expectancy) per death also were calculated for the period 1990-1999. To calculate this index, the total number of all race/sex deaths in each age group was multiplied by the corresponding U.S. population life-expectancy, then summed over all age groups to obtain the total YPLL, and then divided by the total number of deaths for each state during this time period.

Rank Order
For each state, a rank order is presented for each of several mortality measures. Depending on the specific mortality measures, a rank order of "1" indicates the greatest number of deaths, highest mortality rate, or highest YPLL among all states in the U.S.

Most Frequently Recorded Industries/Occupations
In this report, the ten most frequently recorded Bureau of Census industries (CIC) and occupations (COC) with at least two decedents have generally been listed for specified causes of death (from selected states and years in Appendix E). Where more than one industry/occupation was tied for tenth place, all those that were tied were listed.

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 (see Appendix E for a list of states and years for which data qualified).

The PMR is defined as the observed number of deaths with the condition of interest (mentioned as either underlying or contributing) in a specified industry/occupation (from selected states and years in Appendix E), divided by the expected number of deaths with that condition. The expected number of deaths is the total number of deaths in the Bureau of Census industry (CIC) or occupation (COC) of interest multiplied by a proportion 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 five-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). (PMRs presented in the 1999 Work-Related Lung Disease Surveillance Report were internally adjusted for age only, using the age groupings 15-34, 35-54, 55-74, and 75 years and over.) Confidence intervals were calculated assuming Poisson distribution of the data.

A PMR greater than 1.0 indicates that there were more deaths associated with the condition in a specified occupation or industry than expected. This report includes only those industries/occupations with five or more decedents with the condition of interest and a lower 95% confidence limit exceeding 1.0.

MORBIDITY

Prevalence (Asthma, Chronic Obstructive Pulmonary Disease, and Smoking)
The prevalence of asthma, chronic obstructive pulmonary disease (COPD), and cigarette smoking was based on the 2000 NHIS data collected from adult (18 years and older) household interview survey. Asthma was defined as a "yes" response to the question, "Have you ever been told by a doctor or other health professional that you had asthma?" COPD was defined as a "yes" response to either of the following questions: (1) "Have you ever been told by a doctor or other health professional that you had chronic bronchitis?" or (2) "Have you ever been told by a doctor or other health professional that you had emphysema?" Cigarette smoking status was classified as three groups: nonsmokers, current smokers, and former smokers. Nonsmokers were defined as those who smoked less than 100 cigarettes during their entire life. Former smokers were defined as those who smoked at least 100 cigarettes in their entire life and do not currently smoke. Information on current occupation and industry was coded according to the revised 1995 Standard Industrial and Occupational Classification. These detailed occupation and industry codes were collapsed in the NHIS public-use data set (available at www.cdc.gov/nchs/about/major/hdasd/nhdsdes.htm).

Prevalence rates for asthma and COPD were estimated (using sample weights and adjustment for non-responses) by gender, smoking status, industry, and occupation as regrouped by NCHS in the NHIS data files. The prevalence of cigarette smoking was estimated by gender, industry, and occupation. Survey Data Analysis (SUDAAN®) software was used to estimate variances, enabling calculation of 95% confidence intervals for asthma, COPD, and smoking prevalence rates. Lower 95% confidence limits less than zero were converted to 0.0 and upper 95% confidence limits greater than 100 were converted to 100.0.

Prevalence (Coal Workers' Pneumoconiosis)
Prevalence of Coal Workers' Pneumoconiosis (CWP), presented by tenure and time period, was based solely on "final determinations" (consensus values) of ILO category 1/0 or higher of chest radiographs taken for the Coal Workers' X-ray Surveillance Program (CWXSP). Administrative and regulatory guidelines have varied over the life of the program. From 1970 through 1981, the program was administered in structured rounds. After a change in procedure in 1981, examinations have been arranged on a continual basis. For this report, CWXSP data collected after 1981 are grouped into 5-year periods (referred to as "rounds"), which roughly correspond to cycles during which all working underground coal miners could elect to receive a chest x-ray. In cases where more than one chest x-ray was available for a single participant in the same round-usually due to a change in employer-the final determination for the most recent chest x-ray was used. Tenure in underground coal mining was based on summation of years in various mining occupations, as reported by the miner at the time of x-ray.

Incidence Rates (Occupational Respiratory Illnesses)
Estimated numbers of work-related respiratory illness (with days away from work) and incidence rates of occupational respiratory conditions due to toxic agents were generally abstracted from the BLS annual reports of occupational injuries and illnesses, 1992-2000. Where data were not directly abstracted from BLS reports, incidence rates for occupational respiratory illnesses (with days away from work) were computed by dividing the BLS-estimated annual number of incident cases in the industry by the BLS-estimated industry-specific employment for the corresponding year. The resulting quotients were multiplied by 100,000 to yield rates per 100,000 workers.

Association of Occupational and Environmental Clinics (AOEC) Diagnoses
In this report, the frequency distributions of work-related respiratory conditions diagnosed in AOEC clinics and respiratory hazards associated with respiratory diagnoses were tabulated by AOEC from the AOEC database.

Discharges from short-stay nonfederal hospitals (Asbestosis, Coal Workers' Pneumoconiosis, Silicosis)
Estimated numbers of discharges from short-stay nonfederal hospitals were tabulated from the National Hospital Discharge Survey (NHDS) data files provided by the National Center for Health Statistics (NCHS). Estimated numbers were based on any mention of asbestosis, CWP, or silicosis from among the seven diagnosis codes provided in the data files, and for those discharges age 15 years and older.

EXPOSURE

Occupational Exposure Limits
Permissible Exposure Limits. OSHA and MSHA each enforce regulations that establish the legal limits of workplace exposures to pneumoconiotic agents. These legal limits are described in this report as permissible exposure limits (PELs), although the regulations sometimes use the term "standard" or "exposure limit." The current legal limits may be found in the U.S. Code of Federal Regulations (CFR), as follows:

Although OSHA has PELs for the maritime industry [29 CFR 1915], very few samples have been collected and are not reported here.

The OSHA PELs for several pneumoconiotic agents were changed on March 1, 1989, but a legal challenge to the modified OSHA PELs was upheld, and the modified OSHA PELs reverted to the previous OSHA PELs on March 23, 1993. Therefore, data for respirable quartz, selected pneumoconiotic agents, and all pneumoconiotic agents are reported for the three time periods: 1979 to 1988; 1989 to 1992; and 1993 to 1999. Some pneumoconiotic agents had a substance-specific OSHA PEL only from March 1, 1989 to March 22, 1993, including: aluminum as welding fumes, respirable dust of natural graphite, mica containing less than 1% crystalline silica, tin oxide, inorganic compounds of tin oxide, fused respirable silica dust, fibrous talc not containing tremolite, talc not containing asbestos, insoluble tungsten & compounds, and welding fumes (total particulate).

The MSHA metal/nonmetal mining PELs for pneumoconiotic agents were adopted from the 1973 edition of the American Conference of Governmental Industrial Hygienists (ACGIH®) publication entitled TLV®s Threshold Limit Values for Chemical Substances in Workroom Air Adopted by ACGIH for 1973. MSHA has not adopted a PEL for the pneumoconiotic agents: tin oxide dust/fume; inorganic dusts of tin; insoluble tungsten dusts/fumes; and welding fumes (total particulate). In this report a MSHA PEL of 10 milligrams per cubic meter (mg/m³) is used for welding fumes (total particulate) through 1993, but since then it has been MSHA policy not to collect samples for welding fumes.

OSHA and MSHA do not have PELs specific for any form of crystalline silica. The PELs apply to respirable dust containing crystalline silica, and the allowable exposure to respirable dust is reduced as the crystalline silica content increases. The formulas for allowable exposure vary with the agency and the industry. In metal/nonmetal mining, the MSHA PEL is the same as the OSHA PEL for respirable dust containing at least 1% quartz:

However, OSHA adopted a PEL of 0.1 mg/m³ for quartz that was enforced from March 1, 1989 through March 22, 1993.

Since December 1972, the MSHA PEL for respirable coal mine dust has been 2 mg/m³ MRE¹ unless the quartz concentration of the respirable coal mine dust at the mine exceeds 5%. When the quartz content of the respirable dust exceeds 5% in a coal mine sample, the MSHA PEL is reduced based on the following formula:

The OSHA PEL of 2 fibers per cubic centimeter (f/cc) for asbestos was reduced to 0.2 f/cc on July 21, 1986, and to 0.1 f/cc on October 11, 1994. Therefore, asbestos exposures are reported for three time periods: 1979 to 1986; 1987 to 1994; and 1994 to 1999. The MSHA PEL for asbestos has not changed from 2 f/cc since it was adopted.

The OSHA PELs for cotton dust (raw) vary by processing operation. They are:

• 1 mg/m³ for the cotton waste processing operations of waste recycling (sorting, blending, cleaning, and willowing) and garneting;
• 0.75 mg/m³ for textile slashing and weaving operations;
• 0.50 mg/m³ for textile mill waste house operations or for dust from "lower grade washed cotton" used during yarn manufacturing; and
• 0.20 mg/m³ for yarn manufacturing and cotton washing operations.

Reporting of cotton dust data began when the process-specific OSHA PELs became effective on March 27, 1980.

Recommended Exposure Limits. NIOSH develops and periodically revises recommended exposure limits (RELs) for hazardous substances or conditions in the workplace. The RELs are then published and transmitted to OSHA and MSHA for use in promulgating legal standards. The RELs for mineral dusts and chemical hazards, including pneumoconiotic agents, are published in the NIOSH Pocket Guide to Chemical Hazards (NIOSH Pub. No. 97-140). The REL for coal mine dust was adopted in September 1995, while RELs for the other pneumoconiotic agents in this report were adopted before 1979, which is the first year OSHA and MSHA data are reported. The REL for beryllium and compounds is based on cancer, rather than pneumoconiotic effects. NIOSH has no full-shift RELs for the following pneumoconiotic agents: aluminum oxide; emery; synthetic graphite; rouge; fused respirable silica dust; titanium dioxide; and welding fumes (total particulate).

Data Selection
MSHA coal mine dust samples included in this report met all of the following criteria:
(1) obtained in the United States or one of its territories;
(2) designated by MSHA as valid;
(3) coded as "designated occupation," "non-designated occupation," "designated work position," "non-designated work position" with valid occupation codes, or "designated area" other than "intake air."

MSHA Coal Mine Quartz. MSHA coal mine quartz samples included in this report met all of the following criteria:
(1) obtained in the United States or one of its territories;
(2) designated by MSHA as valid;
(3) sample duration greater than zero;
(4) quartz concentration greater than or equal to zero;
(5) coded as "designated occupation," "non-designated occupation," "designated work position," "non-designated work position" with valid occupation codes, or "designated area" other than "intake air."

MSHA Metal/Nonmetal Mine Data (MNMD). MSHA metal/nonmetal mine data (MNMD) included in this report met the following criteria:
(1) obtained in the United States or one of its territories;
(2) not duplicated by another record, as determined by a comparison of all data fields.

NIOSH staff edited the MNMD provided by MSHA to remove duplicate records and records with internal inconsistencies, similarly to the methods previously used by the U.S. Bureau of Mines for data presented in earlier Work-Related Lung Disease Surveillance Reports.

OSHA Integrated Management Information System (IMIS). IMIS samples included in this report met all of the following criteria:
(1) the state code was one of the 50 U.S. states, Washington, DC, American Samoa, Guam, Puerto Rico, or the U.S. Virgin Islands;
(2) the sample type was "area" or "personal" (excludes: "bulk," "wipe," "screen," "blood," and "urine" samples);
(3) the exposure type was "time-weighted average," or "not detected" (excludes: "ceiling," "peak," "dose," "sound reading," "not analyzed," and "not valid");
(4) the indicated OSHA PEL and units were applicable to the contaminant indicated by the substance code for the recorded date of sampling.

Data Analysis for MSHA and OSHA Samples
The reported number of samples for an agent was the total number of samples meeting the above criteria. The percent of samples exceeding the PEL for an agent category was calculated as the number of samples in that category with measured exposures exceeding the PEL enforced at the time the sample was collected, divided by the total number of samples for the agent, and finally multiplying by 100. The percent of samples exceeding the REL for an agent was calculated as the number of samples in that category with measured exposure exceeding the REL, divided by the total number of samples for the agent, and multiplying by 100.

Exposures are commonly log normally distributed, rather than normally distributed. For this reason we present geometric means of the exposure. To calculate a geometric mean exposure, samples less than the minimum quantifiable concentration (MQC) were assigned a value, either the (MQC/2) or (MQC/2^1/2), depending on the distribution of samples that were quantifiable.² The analytical methods used to calculate the MQC for selected pneumoconiotic agents are presented in Table F-2 of Appendix F. The calculation assumes a sample duration of 6 hours for cotton dust, and 7 hours for other agents.

The OSHA and MSHA asbestos MQCs changed during the 1979 to 1999 period; therefore, appropriate MQCs were used for each time period.

OSHA analyzed cotton dust or welding fumes (total particulate) samples by using their standard operating procedure (SOP) for nuisance dusts. The limit of detection of 10 micrograms was determined by the sensitivity of the balance. Results for cotton dust samples below the MQC, 4.3% of all cotton dust samples, could not be assigned to a specific cotton dust processing operation and were not included in Figure 4-4 (2002 Report) and Table 4-11 (2002 Report).

The MSHA respirable coal mine quartz data are based on analyses of respirable coal mine dust samples. However, the quartz content could not be reliably identified for most of these samples. Therefore, in Section 2, the percent of respirable coal mine dust samples exceeding the MSHA PEL were calculated using the MSHA PEL of 2 mg/m³ MRE for respirable coal mine dust containing no more than 5% quartz.

In Section 3 the geometric means of exposure to quartz are reported for OSHA samples. However, the reported percentage greater than the PEL (% > PEL) compares only the respirable dust samples containing at least 1% quartz to the PEL for respirable dust containing at least 1% quartz. The exception is from March 1, 1989 through March 22, 1993, when OSHA enforced a PEL of 0.1 mg/m³ for respirable quartz. During this period the percentage greater than the PEL (% > PEL) compares the exposure to quartz to 0.1 mg/m³.

Industries with Elevated PMRs and Most Frequently Recorded on Death Certificates
This report includes number of samples, geometric mean exposures, and percent of samples exceeding the PEL or REL by selected industries for exposure agents related to elevated occupational lung disease mortality. For asbestosis, CWP, silicosis, byssinosis, and all pneumoconiosis, separate tables present data for the ten most frequently recorded industries with five or more decedents and significantly elevated PMRs.

STATE AND COUNTY DESIGNATIONS

The "number of states" displayed on maps in this report sums to 51 because the District of Columbia is included.

Counties in this report are coded according to the 1990 Federal Information Processing Standards (FIPS) Codes system. A small number of counties or county equivalents have split, merged with, or separated from surrounding or adjacent subdivisions (see Appendix H). Readers should be cautious in assessing geographic patterns and temporal trends for subdivisions that have split or merged.

INDUSTRY/OCCUPATION CODES AND TITLES

Since 1993, the 1990 Bureau of Census (BoC) Index of Industries and Occupations classification system (see "Technical Appendix for 1995" at www.cdc.gov/nchs/about/major/dvs/mcd/1998mcd.htm) has been used for coding death certificate information on the NCHS multiple cause-of-death data files. Most codes and titles in the 1990 system do not differ from the 1980 system. All tables reporting BoC industry (CIC) and occupation (COC) codes and titles that are presented in the mortality and exposure sections of this report, except those listed in Appendix D, follow the 1980 BoC classification system.

Industry/occupation titles ranked by estimated prevalence of asthma, COPD, and smoking, which are presented in the morbidity sections of this report, had been classified according to the 1995 Standard Industrial Classification (SIC) System and then regrouped by NCHS. Incidence rates of the pneumoconioses (including siderosis) and respiratory conditions due to toxic agents follow the 1987 SIC System. Tables summarizing temporal patterns of geometric means in selected exposure sections (i.e., asbestos, silica, and pneumoconiotic agents) of this report also group industries by the 1987 SIC 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 (COC) are grouped by the 1990 BoC classification system.