The Effect Of Changes In Shift Patterns On The Risk Of Pneumoconiosis

Objectives
The overall aim of the study was to investigate how the risks of pneumoconiosis vary for
different patterns of exposure in coalminers. Five exposure scenarios with the following shift
patterns were investigated:
• The baseline. A dust concentration of 3 mg.m-3, for a shift pattern of 5 days/week, 8
hrs/day (and 2 days off).
• Pattern 1. A dust concentration of 2.5 mg.m-3, for a shift pattern of 6 days/week, 8
hrs/day (and 1 day off).
• Pattern 2. A dust concentration of 2.45 mg.m-3, for a shift pattern of 3 days/week, 14
hrs/day (and 3 days off).
• Pattern 3. A dust concentration of 2.5 mg.m-3, for a shift pattern of (1 day on 8 hrs/day)
+ (4 days on 12 hrs/day + 1 day on 8 hrs/day) + (5 days on 8 hrs/day) + (1 day on 8
hrs/day (overtime)).
• Pattern 4. A dust concentration is 0.54 mg.m-3, for a shift pattern of continuous work for
28 days at 8 hrs/day to be followed by 7 days off.
We investigated the influence of the change in shift patterns on the risk of category 2
pneumoconiosis by means of a mathematical model. This model describes the exposuredose relationship, where the dose is the burden of coalmine dust in the human lungs. For
humans, the pulmonary adverse effect of coal dust is the impairment of normal functions of
the alveolar region (i.e. the blood-air barrier). This region is normally kept clean and sterile
by scavenging cells, the macrophages, which ingest foreign matters and clear them from the
lung. However, coal dust is predominantly retained in the interstitial space, i.e. the matrix of
supporting tissue of the lung and therefore is prevented from being removed by
macrophages. The accumulation of coal dust in the interstitial space eventually impairs
normal lung functions.
Main Findings
Our calculations indicate that,
• in all cases, a reduction in the level of airborne concentration with respect to the
different shift patterns ( Pattern 1 to 4) would lead to a reduction in pneumoconiosis in
comparison to the pneumoconiosis level obtained when the airborne concentration is at
3 mg.m-3 while allowing for the shift pattern to change correspondingly.
• when compared to the baseline scenario, Pattern 1 and 3 yield the same level of
pneumoconiosis as the baseline level while pattern 2 and 4 give a much reduced level of
pneumoconiosis.
Our model simulations have also indicated that the clearance of coal dust from the lungs is
also a sensitive factor affecting the risk of pneumoconiosis.
Recommendations
The coal mine dust concentration in the air in coal mines should be reduced according to the
proposed time-weighting model in order to reduce Pneumoconiosis Risk or maintain the level of
risk at the baseline level.