Acknowledgments
The authors wish to thank the operators and service companies (and especially their employees) for participation in the NIOSH Field Effort to Assess Chemical Exposures in Oil and Gas Workers. The authors also thank Corey Butler and James Helmkamp (NIOSH Western States Office) and Charles Hayden and Belinda Johnson (NIOSH Division of Applied Research and Technology) for their efforts and contributions prior to and during the field studies.