A systematic review of occupational exposure to coal dust and the risk of interstitial lung diseases

Figures & data

Table 1. Characteristics and main results of nine epidemiologic studies of lung function and pneumoconiosis among coal exposed individuals, with consideration of the quartz content of the coal

Author, year, country [ref.]	Study design (study period)	Study population: exposed /control	Age (range)	Exposure assessment	Exposure levels and duration	Exposure-response analysis	Outcome (measure)	Covariates accounted for	Result
Casswell 1970 UK [15]	Cross sectional study among deceased coal miners	98/0*	No data	Measurement of recovered lung dust; X-ray diffractometry or fluorescence analysis of mineral matter, including quartz and iron	No data	No	Full sized chest radiograph: modelled mean of 11 readings between 0/– and 3/4. ILO classification 1959.	Quartz	Both coal dust and mineral dust increased in the lungs in relation to radiological score: Coal: β = 0.126 (SD 0.01). Mineral: β = 0.533 (SD 0.04).Correlation between mineral and quartz: r = 0.96.
Seaton 1981 UK [16]	Nested case control from one British colliery. Same mine as in Buchanan et al. 2003	21 cases; 21 controls	No data	Thermal precipitator and MRI gravimetric dust sampling from 1954 to 1978. Cumulative exp. 1974–1978 by occupational group times duration within each group.	Cases: resp. dust 11,478 mg h m^–3 Controls: resp. dust 7173 mg h m^–3 Range exp. duration: ~30,000–70,000 h	Yes	Full sized posterior-anterior chest radiograph: One reader: 1+ change in opacities 1974 to 1978. ILO classification 1972.	Age matched controls, quartz	Cases vs. controls: % coal in resp. dust: 57 vs. 63%, p < 0.05 % quartz in resp. dust: 13 vs. 8%, p < 0.05
Hurley 1982 UK [17]	Cross sectional study, 10 British coal mines	2600/0*	52 (35–65)	Thermal precipitator and MRI gravimetric dust sampling from 1954 to 1978. Cumulative exp. by occupational group times duration within each group.	Mean resp. dust 183 g h m^–3 Mean quartz 8.8 g h m^–3 Mean duration 33 years	Yes	Full sized posterior-anterior chest radiograph, mean of five readers: Opacities 2/1+ (ILO classification 1968).	Quartz	Strong effect of cumulative dust exp. when stratified by cumulative quartz exp. Coal dust has an effect on opacities that cannot be explained by quartz or ash. More rapid progression at very high quartz content
Jacobsen 1982 UK [18]	Nested case control study among 4333 miners from 10 British coal mines. Same mines as in Hurley et al. 1982	45 cases; 41 controls	Cases 43 Controls 44	Thermal precipitator and MRI gravimetric dust sampling from 1954 to 1978. Cumulative exp. by occupational group times duration within each group.	Cases: resp. dust 43 g h m^–3 Controls: resp. dust 38 g h m^–3 Exp. duration >10 years	No	Full sized posterior-anterior chest radiograph: Change: 2+ step (ILO classification 1968)	Smoking, quartz	Mean difference cases vs. controls: Resp. mixed coal dust 5.2 g h m^–3 Quartz 0.75 g h m^–3 Quartz % of mixed coal dust 1% Quartz-related unusually rapid progression of opacities
Ruckley 1984 UK [19]	Cross sectional study among deceased coal miners	261/0*	No data	Measurement of recovered lung dust and infrared spectrophotometry of residual ash, including quartz	No data	No	Full size posterior-anterior chest radiograph: opacities ILO classification 1971). Three gradings of pathological findings: O; 1 (< 1.5 mm); 2 (1.5 –3 mm); 3 (> 3 mm). > 10 mm excluded.	Quartz	Low rank coal: the increase in profusion was most closely related to the ash component of the total dust High rank coal: both coal dust and ash increased in the lungs in relation to radiological profusion
Douglas 1986 UK [20]	Cross sectional study among deceased coal miners	430/0* Autopsied lung pairs. (1972–1974).	No data	Thermal precipitator and MRI gravimetric dust sampling from 1954 to 1980. Average level by occupational group times duration within each group.	Resp. dust 136.9–303.1 g h m^–3 Carbon 81.1–94% Quartz 2.8–5.4% Exp. duration 27–44 years	Yes	Three gradings of pathological findings: 1: < 1 mm; 1–9 mm and 10+ mm lesions	Quartz	Increasing lesions with increased whole dust and ash deposits in the lungs. Not possible to evaluate the quartz effect properly.
Morfeld 1997 Germany [21]	Follow up study. Mean follow-up time 9.3 years, three German coal mines	5778/0*	No data	43,842 gravimetric dust sampling, individual and area measurements.	Mean resp. dust 1.8 mg m^–3 Mean quartz 0.18 mg m^–3 Between 1.7 and 12.5% quartz Mean exp. duration 21.1 years	Yes	Full and small sized anterior-posterior chest radiograph: Opacities 0/1+ (ILO classification 1980)	Quartz	1 mg m^–3 vs. 3 mg m^–3 resp. dust adjusted for quartz dust: RR = 0.98 (p = 0.98) No relationship between coal dust and abnormal radiological finding. Strong ‘mine’ effect not explained by dust or quartz concentration
Buchanan 2003 UK [22]	Cross-sectional study, 1990–1991, one British colliery. One of the 10 mines included in Hurley 1982	371/0*	50–74	Thermal precipitator and MRI gravimetric dust sampling from 1954 to 1980. Average level by occupational group times duration within each group.	Mean non-quartz resp. dust 53.1 g h m^–3 Mean quartz 4.48 g h m^–3 Mean exp. duration 8000 h	Yes	Full size posterior-anterior chest radiograph: Opacities 2/1+ (ILO classification 1980)	Smoking, age, quartz	OR, resp. dust g h m^–3 pre-1964 adjusted for quartz: 0.996 (0.971–1.022) OR, resp. dust g h m^–3 post-1964 adjusted for quartz: 1.025 (0.974–1.079) Absolute risk for 15 years exp. to non-quartz resp. dust: 0.8%
Graber 2014 USA [23]	Follow-up mortality study 1969–2007, underground coal mine workers. Mean follow-up time 20.8 years	8829/0*	Mean 45 at start of follow-up.	Mine safety and health administration compliance data from 1982–2002. Gravimetric sampling. Average level by occupational group times duration within each group.	Mean coal dust 64.6 mg m^–3 year Quartz 2.6 mg m^–3 year	Yes	Pneumoconiosis from death certificates Full size anterior-posterior chest radiograph (ILO classification 1980)	Smoking, age, coal rank, race, calendar year, quartz	Cox proportional hazard analysis. Resp. dust HR adjusted for quartz between 1.17 and 2.58 depending on mine, highest for hard coal mines. Interaction between dust and mine. Quartz HR adjusted for resp. dust: 1.33 (0.94–1.90)

*No internal control group; PMF – Progressive massive fibrosis; FEV1 – forced expiratory volume in one second; FVC – forced vital capacity; FEV1/FVC – ratio FEV1/FVC; ILO – International Labour Organization; RR – relative risk; OR – odds ratio; Resp. – respirable; Exp. – exposure.

Casswell C , Bergman I , Rossiter CE . The relation of radiological appearance in simple pneumoconiosis of coal workers to the content and composition of the lung. Inhaled Part. 1970;2:713–726.

 Google Scholar

Seaton A , Dodgson JA , Dick J , et al. Quartz and pneumoconiosis in coalminers. Lancet. 1981 Dec 5;318(8258):1272–1275.

 Google Scholar

Hurley JF , Burns J , Copland L , et al. Coalworkers’ simple pneumoconiosis and exposure to dust at 10 British coalmines. Br J Ind Med. 1982 May;39(2):120–127.

 Google Scholar

Jacobsen M , Maclaren WM . Unusual pulmonary observations and exposure to coal mine dust: a case-control study. Ann Occup Hyg. 1982;26(8):753–765. DOI:10.1093/annhyg/26.8.753

 Google Scholar

Ruckley VA , Fernie JM , Chapman JS , et al. Comparison of radiographic appearances with associated pathology and lung dust content in a group of coalworkers. Br J Ind Med. 1984 Nov;41(4):459–467.

 Google Scholar

Douglas AN , Robertson A , Chapman JS , et al. Dust exposure, dust recovered from the lung, and associated pathology in a group of British coalminers. Br J Ind Med. 1986 Dec;43(12):795–801.

 Google Scholar

Morfeld P , Vautrin H , Kösters BA , et al. Components of coal mine dust exposure and the occurrence of prestages of pneumoconiosis. Appl Occup Environ Hyg. 1997;12(12):973–979. DOI:10.1080/1047322X.1997.10390637

 Google Scholar

Buchanan D , Miller BG , Soutar CA . Quantitative relations between exposure to respirable quartz and risk of silicosis. Occup Environ Med. 2003 Mar;60(3):159–164. DOI:10.1136/oem.60.3.159

 PubMed Web of Science ®Google Scholar

Graber JM , Stayner LT , Cohen RA , et al. Respiratory disease mortality among US coal miners; results after 37 years of follow-up. Occup Environ Med. 2014 Jan;71(1):30–39. DOI:10.1136/oemed-2013-101597

 PubMed Web of Science ®Google Scholar