LONDRINA, Brazil -- Researchers in Brazil analyzed several studies from around the world that looked at the drug and alcohol habits of truck drivers.
Over half of the participants reported drinking alcohol on the job and some reported using amphetamines, marijuana and cocaine.
The researchers from the State University of Londrina said the number of participants in the study, who were from Australia, U.S., Pakistan and Brazil, was sometimes low and did not represent the whole trucker community.
According to the the American Trucking Associations, however, the research relied only on self-reporting and some biological testing. It said data from the Federal Motor Carrier Safety Administration more accurately shows drug and alcohol use in commercial drivers at closer to 1 percent.
A previous version of this story cited the Journal of Occupational and Environmental Medicine and did not include that other countries were involved in the study.