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Work-Related Lung Disease Surveillance System (eWoRLD)

Methods: State-Based Surveillance


Cases of silicosis from state-based surveillance are confirmed based on the surveillance case definition for silicosis. The silicosis case definition includes 1) an occupational exposure history to airborne silica dust and 2) a positive chest radiograph or other imaging technique for silicosis and/or positive pathologic findings characteristics of silicosis. For more information, see Silicosis State Reporting Guidelines and Case Definition.

State-based information is presented by case ascertainment source, duration of silica exposure, and reported primary industries and occupations of the cases identified. See Industry/Occupation Codes and Titles section below for industry and occupation classifications.

Work-Related Asthma

Cases of work-related asthma (WRA) from state-based surveillance are grouped based on WRA classification criteria into two major types: 1) work-aggravated asthma (WAA) and 2) new-onset asthma (NOA). NOA is further classified as either reactive airways dysfunction syndrome (RADS) or occupational asthma (OA) and its sub-classifications. For more information, see Work-Related Asthma State Reporting Guidelines and Case Definition. In some instances WRA cases may meet the requirements of the surveillance case definition for a confirmed case of WRA without sufficient information for classification. These cases are noted as "Confirmed, but unclassified".

Information is also presented by reported primary industries and occupations. See Industry/Occupation Codes and Titles section below for industry and occupation classifications.

Putative agents associated with cases of WRA are grouped using established Association of Occupational and Environmental Clinics (AOEC) exposure categories and sub-categories1 or combined individual exposure codes. Combined individual exposure codes include Miscellaneous Chemicals and Materials (AOEC codes 320.02320.32, 320.34321.99, 323329.3), Indoor Air Pollutants (AOEC codes 320.01 and 320.33), Mold (AOEC codes 390.01, 390.12, 391.01391.08), and Microorganisms not Including Mold (390.00, 390.02390.16, 391.09391.11, 390.13). These categories contain agents of similar use or chemical nature. The following table shows the AOEC exposure categories and corresponding exposure code prefixes presented in the work-related asthma tables.

AOEC Exposure Categories and Codes
Exposure Categories Exposure Code Prefix*
Miscellaneous chemicals and materials 320.02–320.32, 320.34–321.99, 323–329.3
Mineral and inorganic dusts 010–012
Cleaning materials 322
Pyrolysis products 330–331
Indoor air pollutants 320.01, 320.33
Solvents, n.o.s. 171
Mold 390.01, 390.12, 391.01–391.08
Isocyanates 220–221
Plant material 370–373
Metals and metalloids 020–024
Hydrocarbons, n.o.s. 170
Polymers 270–271
Acids, bases and oxidizing agents 050–052
Aliphatic and alicyclic hydrocarbons 060–061
Aldehydes and acetals 120
Aromatic hydrocarbons 160–161
Animal material 380–382
Ergonomics 360–362
Miscellaneous inorganic compounds 040–042
Halogens (inorganic) 030
Physical factors 350–354
Epoxy compounds 110
Esters 140–142
Halogenated aliphatic hydrocarbons 190–192
Ketones 130
Aliphatic and alicyclic amines 230–233
Alcohols 070
Aliphatic and miscellaneous nitrogen compounds 260–261
Organophosphate pesticides/Carbamate pesticides 290–292
Phenols and phenolic compounds 180–181
Glycol ethers 090–091
Microorganisms, not including mold 390.00, 390.02–390.16, 391.09–391.11, 390.13
Glycols** 080
Organic sulfur compounds** 310–311
Aliphatic carboxylic acids** 150–151
Cyanides and nitriles** 210–211
Ethers** 100
Halogenated aromatic hydrocarbons** 200–201
Aromatic nitro and amino compounds** 250–252
Organochlorine insecticides** 280
Unknown hazard with brand name** 999

n.o.s. - not otherwise specified

* For exposure categories that represent combined individual exposure codes, the full exposure codes are presented.

** Exposure category is aggregated into an "All other exposure categories".

A single case of WRA may be associated with up to three putative agents and as a result may be counted in more than one category. The AOEC designation of agents as occupational asthmagens on the exposure code list is made according to an AOEC protocol (see Revised Protocol: Criteria for Designating Substances as Occupational Asthmagens on the AOEC List of Exposure Codes under Epidemiology Tools: Asthmagen Criteria link at

For each agent, an indication of whether the agent has a high or low molecular weight is presented. Based on the Environmental Protection Agency standards, high molecular weight is defined as a molecular weight greater than or equal to 10,000 Daltons, and a low molecular weight is defined as a molecular weight less than 10,000 Daltons. High and low molecular weights were determined using the Toxicology Data Network for the National Library of Medicine (; NIOSH Pocket Guide to Chemical Hazards (; PubChem Substance (; and Asthma in the Workplace2.

Industry/Occupation Codes and Titles

The primary industries and occupations associated with state-based surveillance silicosis and work-related asthma case data prior to June 2008 updates are grouped by the 1987 Standard Industrial Classification (SIC) system for industries and the 1990 Census Occupation Codes (COC) for occupations. Current presentation of primary industries and occupations are grouped using the 2002 North American Industry Classification System (NAICS), the 2000 COC, and the 2000 Standard Occupational Classification (SOC). Industries and occupations associated with five or more silicosis cases or with 10 or more work-related asthma cases are listed. Industries and occupations associated with less than five silicosis cases or with less than 10 work-related asthma cases are aggregated in an "All other" category.


1 Hunting KL, McDonald SM. Development of a hierarchical coding system for clinic-based surveillance of occupational disease and industry. Appl Occup Environ Hyg 1995;10(4):317–322. (Return to text)

2 Bernstein, IL, Chan-Yeung, M, Malo, JL, Berstein, DI. Asthma in the workplace, 3rd, Taylor and Francis, New York 2006.
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