A deeper look 

at contractor injuries in underground coal mines

by D. Pappas and C. Mark

Deno Pappas and Christopher Mark, 

members SME, are civil engineer and 

mining engineer, respectively, at the 

National Institute for Occupational 

Safety and Health, Pittsburgh, PA. 

Paper number TP-10-062. Original 

manuscript submitted November 

2010. Revised manuscript accepted 

for publication May 2011. Discussion 

of this peer-reviewed and approved 

paper is invited and must be 

submitted to SME Publications Dept. 

by February 28, 2012.

Abstract over the past decade, the number of contractors working in underground coal 

mines has nearly doubled; however, the effect this has had on the industry’s injury rates has 

been the subject of much speculation. The confusion exists because the U.S. mine Safety 

and Health Administration (mSHA) database does not assign contractor hours to the individual 

mining operations where they worked. To better understand the safety record of the contractor 

segment of the industry, the national Institute for occupational Safety and Health (nIoSH) 

undertook a comprehensive analysis of the data contained in the MSHA database. The first 

part of the study compared overall contractor and operator trends from 1983 to 2009 related 

to employment, hours worked and injury rate. One unexpected finding was that the larger 

contractors tended to have higher injury rates than the smaller ones. The second part of the 

study directly addressed the role of contractors on the safety record of 10 large underground 

coal mines. A detailed analysis provided both injuries and estimated contractor hours worked 

at these mines for the period 1992–2007. Comparison between the estimated contractor injury 

rates and the reported operator injury rates at these mines indicated that the contractor injury 

rates were significantly higher at most of the operations studied. However, the industry-wide 

data indicates that contractor and operator injury rates have converged since 2005 and are now 

equivalent.

Introduction

Over the past 27 years, the number 

of contractor workers in underground 

coal mines has increased nearly six-fold. 

In 1983, there were 763 underground 

contractor workers, compared to 5,347 

in 2009. This dramatic increase in the 

contractor workforce has magnified 

the problem of interpreting contractor injury rates and trends and has 

also magnified problems with recording procedures. In 1983, the U.S. Mine 

Safety and Health Administration 

(MSHA) started to compile records of 

contractor injuries, hours worked and 

production data separately from mine 

operator data. While the contractor 

data can provide a valuable insight into 

this large, growing sector of the mining 

industry, they are seldom subjected to 

the same level of scrutiny as the mine 

operator data. Moreover, while MSHA 

does collect contractor hours worked, 

it does not apportion those hours to individual mine sites, which makes it difficult to directly determine contractor 

injury rates at individual mines. As a 

result, the published incident rates and 

productivity statistics for individual 

operator mines may be misleading, because they do not include contractor 

hours worked.

The safety record of the contractor segment of the industry has been 

a concern for some time. In 2001, after 

13 coal miners died in separate West 

Virginia mine incidents, Gov. Bob Wise 

asked David McAteer, the Assistant 

Secretary for Mine Safety and Health 

at the U.S. Department of Labor during 

the Clinton administration, to prepare 

a report on mine safety and health in 

West Virginia. McAteer’s report found 

that 30% of the state’s fatalities in 

2001 were contractor employees. According to McAteer, “because neither 

mine operators nor independent contractors keep records of the amount of 

coal the contract employees produce, 

the accident rates per tons produced at 

companies where a substantial number 

of contractors are employed is hopelessly skewed,” and “since 30% of the 

accidents in southern West Virginia are 

contractor employees, new methods of 

addressing this problem need to be devised.” 

At about this same time (Sept. 18, 

2001), a methane explosion occurred 
at an Alabama mine, resulting in the deaths of 13 miners. 

Although the media’s attention to this tragic incident was 

diverted by the catastrophic Sept. 11 terrorist attacks, the 

Chicago Tribune did provide an in-depth exposé on coal mine 

safety. This article recognized that “growing numbers of coal 

companies hire contractors to supply and supervise miners, 

insulating themselves from the cost of worker accidents and 

deaths. The rate of contractor injuries underground rose 20% 

over the decade since 1992 and comprised a growing share 

of all underground injuries. But MSHA does not collect 

key injury data about contractors, the Tribune found. The 

agency does not gather records showing the number of hours 

contract miners work at each mine, making it impossible to 

identify “dangerous operations” (Jackson and Dougherty, 

2002). However, this issue may be addressed with the proposed Robert Byrd Mine and Workplace Safety and Health 

Act of 2011, which states, “operators shall be responsible for 

reporting on all miners working at such mines regardless of 

their employer, except that independent contractors shall 

only be responsible for reporting on miners in their employ 

or under their direction or authority” (Rockefeller, 2010).

Both of the pivotal reports cited above asked questions 

concerning the effects of contractor injury rates on the coal 

mining industry, and both have yet to be methodically answered. This paper addresses these questions with a twopronged approach. First, it presents a thorough, updated 

analysis of the descriptive data associated with operator 

and contractor production and injury rate trends using the 

MSHA database. Second, a method has been developed that 

allows for reasonably accurate estimates of the contractor 

hours worked at individual large mines. Hopefully, this study 

will provide some clarity to the past and current effects contractor injuries have on the U.S. underground coal industry.

Who are the contractors?

Workers in underground coal mines can be categorized 

into two groupings, those that work for mine operators and 

those that work for contractors. Operators currently employ 

89% of the nation’s underground coal workforce and perform most of the tasks needed in coal removal. Contractors 

compose most of the remaining portion of the workforce. 

According to MSHA 30CFR 45.2 (1996), contractors are 

defined as any person, partnership, corporation, subsidiary 

of a corporation, firm association or other organization that 

contracts to perform services or construction at a mine. Typically, this includes specialty tasks such as performing complex 

equipment repairs, injecting roof sealant materials, sinking 

shafts, rehabilitating high roof fall areas, drilling and installing overcasts, conveyor belts, etc. Mining companies often 

evaluate workers while they are employed by contractors 

prior to offering them permanent employment. In a few circumstances, the whole mining operation is contracted to an 

outside company who manages all facets of the underground 

mining operation. These comprehensive contractor-managed 

mines have coal tonnage assigned to them in the MSHA 

database. For definition purposes, these operations will be 

referred to as contractor-operated mines. Because contract 

work is growing in mining and contractors often do not report individual mine production statistics to MSHA, tracking 

contractor workers’ injuries is becoming more difficult. Now 

that contactors make up over 11% of the underground coal 

workforce, excluding these injuries dilutes the accuracy of the 

operator injury statistics.

Trends in contractor statistics

The descriptive data for the contractor segment of the 

industry were obtained from the MSHA accident injury and 

employment databases (MSHA, 2010). This study examined the closeout data for 1983-2009 for all underground 

bituminous coal mine injuries resulting in death, a permanent disability, days away from work only, days away from 

work with restricted work activity, days of restricted activity 

only or injuries with no lost workdays or restricted activity (degree of injury: 1-6). Injury rates were computed by 

calculating the number of injuries for every 200,000 hours 

worked underground; this number was selected because 100 

full-time miners work approximately 200,000 hours per year. 

Since contractor records were first compiled, the number of 

underground coal contractor workers has increased six-fold 

(Fig. 1), and a very similar trend was found with the number 

of hours worked (Fig. 2). 

Figure 1

Trend in underground contractor employment (MSHA, 1983-

2009).

Figure 2

Trend in underground contractor hours (MSHA, 1983-2009).

It is important to note that while 

contractors represent 11% of all underground coal workers, 

contractor hours were only 6% of all underground hours 

worked in 2009. 

 A 27-year overview of contractor injury rates shows that 

the contractor injury rate initially fluctuated, but stabilized 
around the operator injury rate. From about 1997 to 2003, 

the contractor injury rate was significantly higher than the 

operator rate (Fig. 3). 

Figure 3

Injury rate comparison (MSHA, 1983-2009).

 In some of these years, the contractor injury rate exceeded the operator injury rate by more 

than 35%. Several factors may have contributed to their 

high injury rates. During this period, an older generation of 

miners was retiring, resulting in a new workforce of young 

and inexperienced miners. Many of these new workers first 

entered as contract workers. 

Management practices may also have been changing due 

to the coal boom of 2001. After 20 lean years, the spot market for coal surged to $50 per ton, and suddenly there was 

a big demand for coal and coal miners (Abramson, 2001). 

Along with the generational change, the size of the workforce 

was increasing due to the greater demand for coal. Mining 

companies may have used more contractors to fill in the gaps 

in their workforce to keep up with production demands.1

1 These injury rate differences could also be associated with the 

possibility that contractors and operators may be performing 

diverse tasks with different intrinsic levels of hazard exposure.

Finally, contractor-operated mine injuries peaked during this 

time period.

Since about 2004, however, the contractor injury rates 

have converged with the operator injury rates and, by 2008, 

they were actually lower than the operator rates. Figures 

4-6 provide insight into the age and experience of the injury 

victims. While the demographics (age and experience) of 

the entire contractor and operator workforce are not known, 

the data present some interesting comparative trends. The 

mean age of the victims has been fairly constant for the past 

20 years: around 40 years of age for the operators and 35 

years for the contractors (Fig. 4). 

Figure 4

Comparison of mean victims’ age (MSHA, 1983-2009).

 However, the mean total 

mining experience of the operator victims peaked in 2000 at 

17 years of experience and has been dropping every year to 

11 years of experience in 2009 (Fig. 5). 

Figure 5

Comparison of mean total mining experience of victim 

(MSHA, 1983-2009).

Figure 6

Comparison of mean mining experience of victim at the 

mine were the incident occurred (MSHA, 1983-2009).

 The mean total mining experience of the contractor victims peaked in 1997 at 11 

years of experience and dropped to four years of experience 

in 2008 (Fig. 5). Perhaps this is an indication of the changing 

workforce in underground mines, as the older generation of 

miners retires and is replaced by a younger one. This seems 

to be especially the case for contractor miners, who seem 

to be hired at younger ages than the operator miners and 
hired with less mining experience. Figure 6 shows 

the mean mining experience of the victims at the 

mine where the incident occurred. For the operator workforce, the mean experience at the mine 

peaked at 8.5 years in 1991, dropping to four years 

by 2007. For contractor miners, the consistent average for the past 27 years has been less than one 

year of experience at the mines where the incident 

occurred. 

The MSHA data can also be used to evaluate 

different subgroups within the contractor segment 

of the industry. For this analysis, the contractors 

were grouped into four sizes based on cumulative 

hours worked (1992-2009): 2

2 The period 1992-2009 was chosen in order to focus 

on the years that contractor injuries became more 

commonplace and the injury rates were not so volatile (due to the low numbers in the 1980s).

•	 big contractors, with more than 1 million 

hours worked,

•	 medium-sized contractors, with 200,000 to 

1 million hours worked,

•	 small contractors, with 20,000 to 200,000 

hours worked and 

•	 very small contractors, with less than 

20,000 hours worked. 

An overall grouping of all operator coal mines 

is listed for comparison purposes.

For these five groupings, the number of injuries and hours were compiled and actual injury 

rates were calculated. Figure 7 shows that the 

large contractor grouping, which includes almost 

half of all contractor hours, has had consistently 

— often significantly — higher injury rates than 

traditional coal operators. 

Figure 7

Injury rate by contractor size (MSHA, NIOSH, 1992-2009). 

Note: The “very small contractors” and “contractor-operated 

mines” groupings are not shown due to the large annual 

fluctuations in their injury rates.

 However, within the 

past five years, all four contractor rate groupings 

have converged with operator injury rates (which 

was the case for the overall contractor injury rates 

shown in Fig. 3). 

A comparison of the percentage of injuries 

and hours worked among the four groupings for 

the period 1992-2009 reveals that big contractors 

had 52% of the injuries but account for only 46% 

of the hours worked (Fig. 8). 

Figure 8

Comparison of contractor injuries and hours worked based on 

contractor’s size (MSHA, NIOSH, 1992-2009).

The injury rate for 

the big contractor group exceeded the overall contractor injury rate by 13% and the operator injury 

rate by 21% (Fig. 9). 

Figure 9

Comparison of contractor injury rates based on contractor size (MSHA, 

NIOSH, 1992-2009).

 Most importantly, contractor-operated mines had at least 40% higher injury rates than the overall injury rates for the U.S. 

These contractor-operated mines represent only 
6% of all contractor hours, so the small number of workers 

involved may explain the volatility of the injury rate from 

year to year. The number of contractor-operator mines appears to be on the decline. All other contractor groupings 

had injury rates below the overall contractor injury rate. 

Estimated contractor statistics

The next phase of the study focused on the largest contractors and the mines where they worked. As discussed previously, contractor injury rates for individual mines cannot be 

determined directly, because contractor hours are not apportioned to the individual mines. To obtain indirect estimates 

of contractor hours worked at individual mines, a method 

was developed that uses the mine-specific injury data. The 

key assumption is that for an individual contractor, the percentage of their total reported injuries at a particular mine is 

proportional to the percentage of their total reported hours 

spent at that same mine. Figures 10 and 11 illustrate the 

method using real data. Figure 10 shows that during the period 1992-2007, Contractor 1 had 44 total injuries, 15 of which 

occurred at Mine A. 

Figure 10

Estimating contractor underground hours for Contractor 1 at 

Mine A. Each full bar represents Contractor 1 injuries or hours 

at all mines worked.

Therefore, the ratio of injuries occurring 

at Mine A for Contractor 1 is 15 out of 44, or 34%. Contractor 1 also reported a total of 159,673 hours worked during 

the period. Therefore, we assume that 34% of these hours, or 

54,434 hours, were worked by Contractor 1 at Mine A. This 

process is repeated for each of the other five large contractors that worked at Mine A, and the total hours are summed 

to provide the estimated total contractor hours worked (Fig. 

11) at Mine A. 

Figure 11

Estimating contractor injury rate for Mine A.

 Dividing the total contractor injuries at Mine 

A by the estimated total contractor hours worked provides 

an estimated contractor injury rate for Mine A (Fig. 11). This 

process was duplicated for the other nine largest mines that 

had at least 40 contractor injuries and more than 1,000,000 

total hours worked per contractor for the years 1992-2007. 3

3 It should be noted that with this method, if a contractor works at a given mine for a period of time but does not report any injuries, the 

presence of that contractor at that mine is not known and the contractor hours worked at that mine will be underestimated. In general, however, the larger the mine, the larger the contractor and, the larger the time period being studied, the more accurate the estimate should be.

Table 1 shows that at five of the 10 mines with a large 

contractor presence, the estimated contractor injury rates 

exceeded the operator injury rate by a factor of two or more. 

At three of the 10 mines, when the estimated contractor rate 

is combined with the operator rate (Table 1, last column), the 

combined overall injury rates increase by more than 15%. 

However, this analysis used 16 years of data and included the 

period when contractor injury rates were significantly higher 

than operator rates industry-wide. Since industry-wide contractor injury rates are now very similar to operator rates, it 

is likely that the current discrepancies at individual mines are 

also much smaller.

Conclusions

When contractor injuries were first included in the 

MSHA database in 1983, their impact on industry statistics might have been overlooked as negligible due to their 

small numbers. As the number of contractors working in 

underground coal mines has increased, their safety record 

has become a significant part of the overall industry statistics. 

To investigate contractor injuries, a full review of contractor and operator production data, injuries, rates and injury 

demographics were compiled and compared. A brief summary of this evaluation shows the following for underground 

bituminous coal mining in the United States:
•	 In 2009, contractors represented about 11% of the 

underground workforce, 6% of the hours and 6% of 

the injuries.

•	 The current average age of contractor injury victims 

is about four years younger than that of the operator 

injury victims.

•	 The current average total mining experience of contractor injury victims is about six years less than that 

of the operator injury victims.

Table 1

Estimated contractor injury rates for 10 largest mines (MSHA, NIOSH, 1992-2007).

Mine name No. 

contractors

No. 

operator 

injuries

No. 

contractor 

injuries

All injuries 

associated with 

contractor

Pct contractor 

injuries at this 

mine

Estimated 

contractor 

hours worked

Operator hours

Mine A 6 370 96 543 17.7 1,471,915 16,201,205

Mine B 8 215 70 612 11.4 1,384,242 12,337,135

Mine C 8 252 57 908 6.3 598,890 5,616,096

Mine D 13 184 88 438 20.1 1,792,754 7,909,681

Mine E 4 1,242 56 323 17.3 383,300 17,359,392

Mine F 2 1,189 47 493 9.5 333,630 13,326,313

Mine G 10 474 104 731 14.2 2,331,752 15,888,633

Mine H 8 250 82 1,162 7.1 949,785 3,373,598

Mine I 13 220 54 932 5.8 846,741 3,868,079

Mine J 6 1,423 44 270 16.3 2,637,419 18,988,067

All UG 

coal 

mines

1,703 76,808 4,122 4,122 100.0 63,599,990 1,351,471,594 

Mine name

Contractor injury 

rate (injuries/200 

khrs)

Operator injury 

rate (injuries/200 

khrs)

Ratio contractor rate/

operator rate

Estimated total injury 

rate (injuries/200 khrs)

Ratio-estimated total 

injury rate/operator 

injury rate1

Mine A 13.0 4.6 2.86 5.3 1.15

Mine B 10.1 3.5 2.90 4.2 1.19 

Mine C 19.0 9.0 2.12 9.9 1.11

Mine D 9.8 4.7 2.11 5.6 1.21

Mine E 29.2 14.3 2.04 14.6 1.02

Mine F 28.2 17.8 1.58 18.1 1.01

Mine G 8.9 6.0 1.50 6.3 1.06

Mine H 17.3 14.8 1.17 15.4 1.04

Mine I 12.8 11.4 1.12 11.6 1.02

Mine J 3.3 15.0 0.22 13.6 0.91

All UG coal 

mines 13.0 11.37 1.14 11.4 1.01

1 This ratio indicates the proportion that the overall total injury rate (includes operator and estimated contractor 

rate) is underreported when compared to the operator injury rate.

•	 The current average mining experience at the mine 

where the incident occurred is less than one year for 

contractors and four years for operator victims.

•	 Contractor injury rates peaked in 2000-2003, when 

they were more than 35% higher than operator injury rates. 

•	 Big contractors had higher injury rates than small 
contractors, though in the past six years these rates 

have also converged.

•	 Peak contractor injury rates seem to coincide with 

the years when the contractor-operated mines had 

high injury rates.

•	 A unique approach to estimate contractor hours 

worked at 10 mine sites with a large contractor presence was developed for the years 1992-2007. Five 

of these 10 mines had estimated contractor injury 

rates that exceeded the operator injury rate by a factor of two. Three of these 10 mines had a combined 

estimated contractor and operator injury rates that 

exceeded the actual operator injury rate by more 

than 15%.

Based on the five most recent years of data, it appears 

that contractor injury rates are now very similar to operator 

injury rates, and the alarmingly high rates of the 2000-2003 

period have significantly improved. The causes of the poor 

safety record compiled by contractors in the early years of 

the last decade may have been related to the drastic employment changes that were occurring in the underground coal 

mines at that time and the reduction of contractor-operated 

mines. These recent lower injury rates appear to indicate 

that contractor worker safety has significantly improved. 

However, other factors may be partially responsible for the 

improvement, such as overall progress in safety intervention 

techniques (i.e., screening, bolting equipment, etc.), reduction in contractor exposure to hazardous activities and more 

experienced contractor miners.

Without records of contractor hours spent at individual 

mine sites, it is not possible to accurately calculate the effects 

of contractor injuries on the mine’s overall injury rate. Until 

such data becomes available, it is hoped that studies like this 

may shed some light on independent contractor injury trends 

in the underground coal mine industry. 

Disclosure

The findings and conclusions in this paper have not been 

formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to 

represent any agency determination or policy.

References

Abramson, R., 2001, “New coal isn’t old coal,” The Alicia Patterson Foundation website, http://www.alicia patterson.org/APF2001.html.

Jackson, D. and G. Dougherty, 2002, “The human cost of coal mining,” third 

part of 3 parts, Chicago Tribune, September 24, http://www.usmra.

com/mine5_3.html.

McAteer, D., 2001, Report to Governor Bob Wise on Mine Safety and Health 

in West Virginia and Recommendations to Make West Virginia Mines 

the Safest and Healthiest in the Nation, Fall 2001, http://www.wvminesafety.org/Mcateer.pdf.

MSHA, 1996, 30CFR 45.2, http://www.msha/regs.htm.

MSHA, 2010, Accident, Illness and Injury and Employment Self-Extracting 

Files (Part 50 Data), 1983-2009, Denver: U.S. Department of Labor, 

Mine Safety and Health Administration, Office of Injury and Employment Information. Date accessed: July 2010.

Rockefeller, J., 2011, The Robert C. Byrd Mine and Workplace Safety and 

Health Act of 2011, U.S. Senate, http://www.theorator.com/bills/text/

s153.html.