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Results of Epidemiologic Studies on the Progression of Coal Workers' Pneumoconiosis
Results of Epidemiologic Studies on the Progression of Coal Workers' Pneumccenicsis" Manfred T. R. Rei8ne1', Dr. Lng.
Epidemiologic studies on pneumoconiosis in West German coal mines are based on dust exposure datat recorded monthly on cards for each miner since 1954, and readings of x-ray film carried out in successive intervals of one to three years. Up to now, data on more than 18,000 miners from 13 collieries have been collected. Periods of up to 14 years of known dust exposure have been analyzed. One of the outstanding results of these studies is the evidence that the development of simple pneumoconiosis is mainly due to a dose-response relationship, and the residence time of the dust retained in the lungs. These findings led to the fixing of a so-called MAK-valuet for quartz-containing respirable dust over a five-year period. Subsequent studies have been concentrated on the progression of existing radiologic changes of simple pneumoconiosis. The first preliminary results can be summarized as follows: miners who showed doubtful (Z ) or slight radiologic changes (ILO categories 1 and 2) within a short period have clearly progressed as a function of further dust exposure. It can be assumed that most of these miners are susceptible to pneumoconiosis and that they also react in a clearly dose-dependent manner during further dust exposure. Restricting dust exposure in miners with simple pneumoconiosis thus fulfllls the purpose of protecting them from further health damage. However, the progression of simple pneumoconiosis is also affected by the after-effects of earlier dust deposition. This can be demonstrated by the influence of the duration of previous dust exposure, as
well as of the cumulative dust exposure in that period and of the mean time of residence of the respirable dust deposited and retained in the lungs. Because of this after-effect the progression of pulmonary changes cannot be completely prevented, even if any further dust exposure is stopped In the groups with the lowest observed dust exposure, about 40 to 50 percent of miners with doubtful radiologic changes still progressed within seven years, depending on the duration of the previous dust exposure. For categories 1 and 2, the corresponding values were about 15 to 35 percent and about 20 to 25 percent.
·Steinkohlenbergbauverein, Essen, West Germany. Reprint requem: Dr. Heimef'~ Bet'gbau-FonchUng GmbH~ Ff'anzi-FitJchef'-Weg 61, D-4300 Essen 13, West GematInv
Previous dust
tcumulative dust exposure value:
"i n (c. • s.)
i -
i
= 1
=respirable dust concentration in mg/ms S = number of shifts worked c
n = number of months iMAK = Maximale Arbeitsplatzkonzentration, maximum permissible concentration of a gas, vapor or· particulate matter in the air within a working area, comparable with the threshold limit values in the U.8.
•
IIlNFRED T. R. REISNER
Table I--Pro.....ora from, Cate.ory 1 (by Year.) wialain 7 Year. 01 Prel1ioua DaaI EsptMure ared CumultdiH ".., Yaluea of FurelaerEspoaure Years of previous dust exposure
Cumulative dust exposure ~ (c-B) in 7 years 0 - 9,500 14,200 - 22,000 and more No. No. No. % % % No. %
<13
1716 17.0
709 21.9
613 29.9 534
35.0
13-26
3944 22.7 1112 24.3
653 30.2 311
26.4
>26
1227
36
36.1
1392 31.3 SSI
32.0
all
34.7
215 33.5
6887 23.3 2036 24.4
126 44.4
No. ==number of cases in category 1 %==percentage progressing from category 1
Table 2--Pro.,.eaion from Cate.oryl wi,lain 7 Y ..... by Cumldadl1e Dua' Yaluea of Prel1ioua and FUrllaer Es"."re
exposure ~
(c-8)
Cumulative dust exposure ~ (c-B) in 7 years 0 - 9,500 14,200 - 22,000 and more No. No. % No. % No. % %
<40,500
214 14.5
76 15.8
37 21.6
13
38.5
>40,500
18 27.8
15 33.3
52 34.6
78
51.3
232 15.5
91 18.7
89 29.2
91
49.5
all
No. ==number of cases with category 1 %==percentage progressing from category 1
CHEST, 78: 2, AUGUST, 1980 SUPPLEMENT
The percentage of progression decreases generally with severity of initial radiologic signs. This may indicate a deceleration of the development of pneumoconiosis to higher categories. With a higher category of simple pneumoconiosis and with a longer duration of the previous dust exposure, the clarity of the dose-response relationship decreases. It may be that miners who showed relatively late radiologic signs of pneumoconiosis represent a selection of more resistant persons who continue to react only weakly to the dose received. These relations are further affected by Q variable after-effect of very different but no well known previous dust exposures.
CHEST, 78: 2, AUGUST, 1980 SUPPLEMENT
The entirely missing influence of the duration of the previous dust exposure on the progression of category 2 gives reason to expect that possibly endogenous factors independent from dose are more and more responsible for the development of more severe pulmonary changes. Studies on individual factors inHuencing pneumoconiosis will shed further ltght on this subject. The continuation of the epidemiologic studies covering a period of at least 20 years of known individual dust exposure will make it possible to confirm the relationships found so far to place the results on a more secure basis, and to include further factors of influence in the analysis.
COAL WORKERS' PNEUMOCONIOSIS 407
Epidemiologic studies on pneumoconiosis in West German coal mines are based on dust exposure datat recorded monthly on cards for each miner since 1954, and readings of x-ray film carried out in successive intervals of one to three years. Up to now, data on more than 18,000 miners from 13 collieries have been collected. Periods of up to 14 years of known dust exposure have been analyzed. One of the outstanding results of these studies is the evidence that the development of simple pneumoconiosis is mainly due to a dose-response relationship, and the residence time of the dust retained in the lungs. These findings led to the fixing of a so-called MAK-valuet for quartz-containing respirable dust over a five-year period. Subsequent studies have been concentrated on the progression of existing radiologic changes of simple pneumoconiosis. The first preliminary results can be summarized as follows: miners who showed doubtful (Z ) or slight radiologic changes (ILO categories 1 and 2) within a short period have clearly progressed as a function of further dust exposure. It can be assumed that most of these miners are susceptible to pneumoconiosis and that they also react in a clearly dose-dependent manner during further dust exposure. Restricting dust exposure in miners with simple pneumoconiosis thus fulfllls the purpose of protecting them from further health damage. However, the progression of simple pneumoconiosis is also affected by the after-effects of earlier dust deposition. This can be demonstrated by the influence of the duration of previous dust exposure, as
well as of the cumulative dust exposure in that period and of the mean time of residence of the respirable dust deposited and retained in the lungs. Because of this after-effect the progression of pulmonary changes cannot be completely prevented, even if any further dust exposure is stopped In the groups with the lowest observed dust exposure, about 40 to 50 percent of miners with doubtful radiologic changes still progressed within seven years, depending on the duration of the previous dust exposure. For categories 1 and 2, the corresponding values were about 15 to 35 percent and about 20 to 25 percent.
·Steinkohlenbergbauverein, Essen, West Germany. Reprint requem: Dr. Heimef'~ Bet'gbau-FonchUng GmbH~ Ff'anzi-FitJchef'-Weg 61, D-4300 Essen 13, West GematInv
Previous dust
tcumulative dust exposure value:
"i n (c. • s.)
i -
i
= 1
=respirable dust concentration in mg/ms S = number of shifts worked c
n = number of months iMAK = Maximale Arbeitsplatzkonzentration, maximum permissible concentration of a gas, vapor or· particulate matter in the air within a working area, comparable with the threshold limit values in the U.8.
•
IIlNFRED T. R. REISNER
Table I--Pro.....ora from, Cate.ory 1 (by Year.) wialain 7 Year. 01 Prel1ioua DaaI EsptMure ared CumultdiH ".., Yaluea of FurelaerEspoaure Years of previous dust exposure
Cumulative dust exposure ~ (c-B) in 7 years 0 - 9,500 14,200 - 22,000 and more No. No. No. % % % No. %
<13
1716 17.0
709 21.9
613 29.9 534
35.0
13-26
3944 22.7 1112 24.3
653 30.2 311
26.4
>26
1227
36
36.1
1392 31.3 SSI
32.0
all
34.7
215 33.5
6887 23.3 2036 24.4
126 44.4
No. ==number of cases in category 1 %==percentage progressing from category 1
Table 2--Pro.,.eaion from Cate.oryl wi,lain 7 Y ..... by Cumldadl1e Dua' Yaluea of Prel1ioua and FUrllaer Es"."re
exposure ~
(c-8)
Cumulative dust exposure ~ (c-B) in 7 years 0 - 9,500 14,200 - 22,000 and more No. No. % No. % No. % %
<40,500
214 14.5
76 15.8
37 21.6
13
38.5
>40,500
18 27.8
15 33.3
52 34.6
78
51.3
232 15.5
91 18.7
89 29.2
91
49.5
all
No. ==number of cases with category 1 %==percentage progressing from category 1
CHEST, 78: 2, AUGUST, 1980 SUPPLEMENT
The percentage of progression decreases generally with severity of initial radiologic signs. This may indicate a deceleration of the development of pneumoconiosis to higher categories. With a higher category of simple pneumoconiosis and with a longer duration of the previous dust exposure, the clarity of the dose-response relationship decreases. It may be that miners who showed relatively late radiologic signs of pneumoconiosis represent a selection of more resistant persons who continue to react only weakly to the dose received. These relations are further affected by Q variable after-effect of very different but no well known previous dust exposures.
CHEST, 78: 2, AUGUST, 1980 SUPPLEMENT
The entirely missing influence of the duration of the previous dust exposure on the progression of category 2 gives reason to expect that possibly endogenous factors independent from dose are more and more responsible for the development of more severe pulmonary changes. Studies on individual factors inHuencing pneumoconiosis will shed further ltght on this subject. The continuation of the epidemiologic studies covering a period of at least 20 years of known individual dust exposure will make it possible to confirm the relationships found so far to place the results on a more secure basis, and to include further factors of influence in the analysis.
COAL WORKERS' PNEUMOCONIOSIS 407