This was a cross-sectional study in design undertaken at ICMR-Centre for Ageing & Mental Health (ICMR-CAMH), Kolkata (previously Regional Occupational Health Centre, Eastern) after obtaining the approval from the Institutional Ethics Committee. The duration of the study was from December 2016 till March 2019.

These study sites were at an approximate distance of 200 km from Kolkata, the capital city of West Bengal and the investigation was conducted among coal mine workers in the Nimcha colliery (Satgram area, ECL) and Ningha colliery (Sripur area, ECL). Both sites had a stable population base with insignificant in or out-migration. Till the completion of the study up to March 2019, 202 coal mine workers were recruited and screened by ASSIST. Following screening by ASSIST 69 per cent (n=140) were found with either ‘hazardous and harmful’ (moderate risk); or ‘dependent’ (high risk) patterns of use of either tobacco or alcohol or cannabis or more than one substance. Only 31 per cent (n=62) were ‘low-risk’ for all substances and were provided with general medical advice including advice to remain at a ‘low-risk’ level for substance use.

All participants were males aged 25 to 58 yr, and the mean age was 46 yr (± standard deviation). Most subjects (about 60%) were illiterate or had only primary education; however, the children of most participants (81%) had either completed school or were currently going to school. The median monthly earnings of workers was INR 35,000, with a range of INR 8,000 to 60,000, and most (88%) had more than one asset in their households. Use of liquid petroleum gas (LPG) (47%) and coal (48%) for cooking were reported by an almost equal proportion of the participating workers.

In screening by ASSIST for patterns of tobacco consumption (both smokeless and smoked), 65 per cent (n=132) participants of 202 belonged to ‘hazardous and harmful’ (moderate risk) and ‘dependent’ (high risk) pattern of consumption. However, about 18 per cent (n=36) participants had only tobacco as the major substance use problem.

Regarding alcohol consumption almost 49 per cent (n=99) workers had ‘hazardous and harmful’ (moderate risk); or ‘dependent’ (high risk) pattern of consumption; 3 participants (1.5%) had only alcohol as the major substance problem.

Only 13 (6.4%) workers were identified with cannabis use with 4.45 per cent (n=9) in ‘hazardous and harmful’ (moderate risk) category and 2 per cent (n=4) were in ‘dependent’ (high risk) category.

When combined substance use was considered, the most common pattern was combined ‘hazardous and harmful’ (moderate risk) or ‘dependent’ (high risk) use of alcohol and tobacco: 31 per cent (n=63) followed by combined moderate to high risk use of alcohol, tobacco and cannabis: 5.45 per cent (n=11).

Screening for anxiety and depression by HADS was conducted to assess the possibility of psychiatric comorbidity among the coal mine worker participants. Anxiety and depression were analyzed upon 132 and 131 participants, out of 202 participants, respectively including all categories, i.e., ‘low-risk, ‘hazardous and harmful’ (moderate risk); or ‘dependent’ (high risk) following adjustment for missing data. Almost 28.8 per cent (n=38) out of 132 participants with any category of alcohol and/or tobacco use as screened by ASSIST were identified with anxiety that included both moderate and high levels of anxiety. Out of the 38 participants who had anxiety, 52.6 per cent (n=20) were moderate to high-risk users of both alcohol and tobacco, while among workers with low risk to both alcohol and tobacco, anxiety was recorded only in 13.2 per cent (n=5). This association was found to be significant both in bivariate and multivariable analysis. Odds of having anxiety was 4.048 times (P=0.029) and 4.896 times (P=0.015) more among participants having moderate to high risk for either alcohol or tobacco use and moderate to high risk for combined alcohol and tobacco use, respectively in comparison with low risk of substance problem (both alcohol and tobacco). Majority of the participants having anxiety (64.3%) had monthly income level less than INR 33,000 and half of the participants (50%) with anxiety were less than 45 yr of age. No significant difference was observed between anxiety with income level and age group (Table I).

Among 131 participants, 23.7 per cent (n=31) were recorded to have depression. Out of the total participants who were depressed, 61.3 per cent (n=19) were in the moderate to high risk for combined alcohol and tobacco use category. Again, among workers with low risk to both alcohol and tobacco depression was only 16.1 per cent (n=5). Combined moderate to high use of both alcohol and tobacco use emerged as risk for having depression [adjusted odds ratio (AOR)=5.335, P<0.012] compared to both low level of alcohol and tobacco use. About 65.2 per cent and 44.8 per cent of participants having depression had income level less than INR 33,000 and belonged to age group of more than 45 yr respectively. No significant association was found between depression with income level and age group (Table II).

This study presents observations regarding patterns of common substance use behaviour among coal mine workers in West Bengal. Alcohol and tobacco were major substance use problems among coal mine workers. Although this study had a small sample size, the prevalence rates for both tobacco and alcohol problems among coal mine workers are much higher than that observed in the general population, viz., 20.9 per cent prevalence of tobacco use disorders and a national prevalence rate of 4.7 per cent of alcohol use disorder among Indian adults identified by National Mental Health Survey 2015-2016¹¹.

Alcohol and other substance use, particularly among different occupation groups, is an under-investigated area in the Indian context, although the health and economic consequences of the same are significant. Available evidence from the country does not report a systematic and robust investigation on alcohol and substance use problems among coal mine workers in India. Reported findings include presence of alcohol use (20%) and tobacco smoking (60%) among stone mine workers in Rajasthan¹² and a higher risk of injury among underground coal miners who consume alcohol⁶. Internationally the evidence base is more robust and comparable to our findings with a cross-sectional study from Mongolia reporting a 22.1 per cent alcohol use among mine workers vs. the national prevalence rate of 15.5 per cent¹³. An Australian study among metal mine workers assessed alcohol use among workers with WHO validated Alcohol Use Disorders Identification Test (AUDIT) and identified a 94.8 per cent alcohol use among males and 92.1 per cent use among females in past 12 months¹⁴. Additionally, a study from Ukraine identified that current drinkers have a higher chance of engagement in a high-risk profession like coal mining¹⁵. The population with moderate to high-risk alcohol use is expected to benefit most from early community or primary care based brief intervention with add on pharmacotherapy.

Combined moderate to high use of both alcohol and tobacco use emerged as risk for having anxiety and depression compared to both low risk of alcohol and tobacco use. In addition, odds of having anxiety is 4.048 times higher among participants having moderate to high risk use of either alcohol and tobacco when compared to low risk of alcohol and tobacco use. Similar observations have also been reported from a study among Chinese coal mine workers with detection rates of anxiety higher among workers with drinking habit¹⁶. A study among Brazilian coal miners, however, reported low rates of depression and 13 per cent prevalence of low or moderate anxiety¹⁷. On the contrary, among Asian population, among Chinese coal mine workers, a study using Hamilton Anxiety Rating Scale and Hamilton Depression Rating Scale identified incidence of anxiety and depression as 51.1 per cent and 60.5 per cent respectively¹⁶. Tobacco is evidenced to possibly have a bidirectional relationship with anxiety or depression with smoking behavior leading to later onset of anxiety/depression or vice versa¹⁸. Similarly alcohol use disorders are known to co-exist at a higher rate among persons with an anxiety disorder or other behavioral disorder¹⁹.

Therefore, our findings not only strengthen the need for community and primary care-based intervention for tobacco and alcohol use disorders among coal mine workers, but further expand the scope of the study to further investigate and intervene for co-morbid common mental health problems.

The resources and time available with the study team did not permit covering a wider representation of the entire coal miner workforce of the Eastern Coalfields Ltd under the present investigation. Our inquiry on mental health comorbidity was limited only to anxiety and depression and we could not include other relevant mental health morbidities. The broad objective of this investigation was to identify whether the study population had a considerable problem of alcohol and other substance use and associated common mental health comorbidities. However, this study was not powered enough to look into the sociocultural determinants to identify the interactions and mediations to investigate further the pathways of substance use disorders and mental health comorbidities.