title: Exposure-response relationships for the ACGIH threshold limit value for hand-activity level: results from a pooled data study of carpal tunnel syndrome.
abstract: OBJECTIVE
  This paper aimed to quantify exposure-response relationships between the American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV) for hand-activity level (HAL) and incidence of carpal tunnel syndrome (CTS).
  
  
  METHODS
  Manufacturing and service workers previously studied by six research institutions had their data combined and re-analyzed. CTS cases were defined by symptoms and abnormal nerve conduction. Hazard ratios (HR) were calculated using proportional hazards regression after adjusting for age, gender, body mass index, and CTS predisposing conditions.
  
  
  RESULTS
  The longitudinal study comprised 2751 incident-eligible workers, followed prospectively for up to 6.4 years and contributing 6243 person-years of data. Associations were found between CTS and TLV for HAL both as a continuous variable [HR 1.32 per unit, 95% confidence interval (95% CI) 1.11-1.57] and when categorized using the ACGIH action limit (AL) and TLV. Those between the AL and TLV and above the TLV had HR of 1.7 (95% CI 1.2-2.5) and 1.5 (95% CI 1.0-2.1), respectively. As independent variables (in the same adjusted model) the HR for peak force (PF) and HAL were 1.14 per unit (95% CI 1.05-1.25), and 1.04 per unit (95% CI 0.93-1.15), respectively.
  
  
  CONCLUSIONS
  Those with exposures above the AL were at increased risk of CTS, but there was no further increase in risk for workers above the TLV. This suggests that the current AL may not be sufficiently protective of workers. Combinations of PF and HAL are useful for predicting risk of CTS.
authors.affiliation: Department of Occupational Science & Technology University of Wisconsin, Milwaukee, PO Box 413 Milwaukee, WI 53201, USA. kap@uwm.edu.
authors.forename: Jay M
authors.initials: JM
authors.lastname: Kapellusch
authors.forename: Frederic E
authors.initials: FE
authors.lastname: Gerr
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Malloy
authors.forename: Arun
authors.initials: A
authors.lastname: Garg
authors.forename: Carisa
authors.initials: C
authors.lastname: Harris-Adamson
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Bao
authors.forename: Susan E
authors.initials: SE
authors.lastname: Burt
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Dale
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Eisen
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Evanoff
authors.forename: Kurt T
authors.initials: KT
authors.lastname: Hegmann
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Silverstein
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Theise
authors.forename: David M
authors.initials: DM
authors.lastname: Rempel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D002349:Carpal Tunnel Syndrome / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D012307:Risk Factors; D020711:Threshold Limit Values; D055815:Young Adult