The basic argument made by DARRPP for random testing is a
safety one: violating employee privacy rights is warranted because random
testing will make workplaces safer. Preparing for the interview, I read a
number of studies that (to my surprise) indicate (1) random drug testing (as
distinct from other kinds of drug testing) is not generally associated with a
reduction in injuries and (2) drug use (as distinct from alcohol use) on the
job or off is not associated with an increase injuries. This seems to undercut
the safety argument almost entirely, which was the message I delivered on the
show.
Since then, I’ve had a fair number of emails and phone calls
with people asking about the evidence. This is a complicated request: (1) there
are many studies, and (2) designing and executing a study often entails
significant tradeoffs so sometimes findings require some expertise to
understand. There is also the matter that it is not possible to prove a
negative (i.e., that drugs never cause injury rates to go up and that random
drug testing never causes injury rates to go down). Rather, we typically
require those who assert a relationship (i.e., DARRP) to show evidence that it
exists, so let’s start there.
The DARPP website cites two studies. The first indicates
random alcohol testing of drivers in the US transport industry reduced fatal
crashes by 23% among large trucks. DAARPP doesn’t tell us which study that is
and I didn’t run across it. But the question at hand is whether illicit drug
testing (not alcohol-testing) reduces injuries, so this study has no real
bearing on the issue.
The DARRPP website cites another US study that shows
mandatory alcohol and drug testing reduces positive tests by 50%. Again, I
couldn’t find the study but let’s assume this is correct. The question is whether
a reduction in positive test results is associated with any difference in
injury outcomes? On this, we have no information. As drug tests measure prior use
(but not impairment), positive tests might have little to do with workplace
injury rates. Or the reduction might indicate gaming behaviour (“Psst. Buddy,
can I borrow some urine?”). If so, a reduction in positive tests is largely
meaningless.
DARRPP also kindly sent me a press release about a 2001
study they thought I should look at: Gerber, J. and Yacoubian, G. (2001).
Evaluation of drug testing in the workplace: A study of the construction
industry. Journal of construction
engineering and management. 127(6): 438-444. While this study found that
firms that implemented drug testing saw a 51% reduction in injury incident rates,
there was no indication that these results stemmed from random drug testing (as
opposed to pre-employment, reasonable cause and post-incident testing—none of
which are the subject at hand). This study also has a small sample and poor
response rate. Overall, this study really tells us nothing useful about the
impact of random drug testing on workplace injuries.
I looked back through my notes and browser history and
started to pull together what I reviewed for the CBC interview. Rather than
attempt a half-assed systematic review, what I’ve done is selected those
articles which present such reviews themselves. This should allow anyone who is
keen to do so, the ability to go back and review each article on their own.
Institute of Medicine (1994) Under the Influence? Drugs and the
American Work Force. Washington: National Academy Press. This book-length
review is one of the better reads, despite the relative age. It found no good
studies on the effectiveness of random drug testing (pp. 226-227). The effect
of a drug in a laboratory varies and can be either positive and negative
(depending on dose and testing). It is difficult to transfer this knowledge to
determine the impact of drug use in the workplace. There was too little data to
indicate that drug use was associated with increase injury and it is unclear if
there is a causal relationship (i.e., some other factor may be at play).
A slightly more recent review is Macdonald, S. (1997).
Work-place alcohol and other drug testing: A review of the scientific evidence.
Drug and alcohol review. 16(3):
251-259. This article also indicates that there was little evidence for a
linkage between drug use and workplace injury and no evidence drug testing
significantly reduces workplace injury.
Overall this literature is difficult to evaluate, and probably inadequate to reach a definitive conclusion. If drug use is associated with work-related injury it appears to be more apparent among males, possibly more likely to occur with cocaine use, and possibly only occurs in certain situations such as when driving or in other ‘high risk’ work. Further, while a slim majority of studies appear to show an association of some sort, even within these studies this does not necessarily constitute causation. (pp. 13-14)
The authors found the evidence also too slim to know if drug
use at work or immediately before a workplace injury increased the risk of
injury. On the question of whether drug testing of any type affected workplace
injuries, the studies were too weak to say anything definitive.
Moving onto actual studies, one of the larger studies is Hoffman, J. and
Larison, C. (1999) Drug use, workplace accidents and employee turnover. Journal of drug issues. 29(2): 341–364.
This study used nationally representative US data to find that drug use in
general is not associated with a higher risk of workplace injury, with little
indication of any such relationship in higher risk occupations such as
construction, transportation and skilled labour.
An interesting study is Macdonald, S. (1995). The role of drugs in
workplace injuries: Is drug testing appropriate? Journal of drug issues, 25(4):
703–23. This study uses self-reports to conclude illicit drug use is not a
major cause of job injuries. This study seeks to control for (and understand)
the impact of other variables on the relationship between drugs use and
injuries—a failing of many other studies.
One of the studies that is sometimes cited as indicating
random testing is effective is Miller, T., Zaloshnja, E. and Spicer, R. (2007).
Effectiveness and benefit-cost of peer-based workplace substance abuse
prevention coupled with random testing. Accident
analysis and prevention. 39(3): 565-573. A careful read shows that the
interactive effect of peer-based interventions and random drug testing was
associated with a one-third drop in workplace injuries. The authors note that
is not possible to disentangle the effect of the two interventions (peer
intervention and random drug testing). The time series data shows the vast
majority of the reduction followed the peer intervention; injury data is
effectively flat after random testing starts. It may be the threat of testing
may have contributed to willingness to participate in peer intervention, but we
don’t know that.
Another construction-specific survey is Olbina, S., Hinzo,
J. and Arduengo, C. (2011). Drug testing practices in the US construction
industry in 2008. Construction management
and economics. 29(10): 1043-1057. This study reports a statistically
significant relationship between positive random drug tests and higher injury
rates, suggesting drug use can increase the change of injury. There were a
number of limitations noted in the study: 14% response rate, with only
two-third using random testing, small sample size (53 firms), and a bias
towards larger firms. An average of 2.23% of random tests were positive,
suggesting illicit drug use is minimal.
The question I’m left is this: if there is no evidence that random
drug testing reduces workplace injury rates, why would employers spend money on
it?
There are several possible answers. They may have been sold a bill a
good by companies that do the random testing. The notion that testing will reduce
injuries accords with most people’s (incorrect) common-sense reaction that testing
should reduce injury rates so that would be an easy enough sell.
Or there may be some other agenda at play. Testing may dissuade drug
users from working at places with testing. If drug-use is associated with other
undesirable behaviours (e.g., propensity to quit), then perhaps random testing
is really about winnowing out these workers.
Testing also implicitly blames workers for workplace injuries, taking
the heat off employers for organizing work unsafely and off the government for
doing a poor job of enforcing the rules. And it makes it look like employers
are doing something about the problem of workplace injuries. There is also a
strong moral dimension to the issue of drug testing that can sometimes cloud
people’s judgment.
Or perhaps these companies just believe (contrary to the
evidence) that testing works. They are certainly entitled to believe that.
Except that testing is a huge invasion of workers’ privacy and is demeaning, so
ought to occur only when there is some evidence of its efficacy at increasing
safety. Absent such evidence, the case for random testing looks pretty weak.
-- Bob Barnetson