The ACGIH TLV for Low Back Risk - Fundamentals and Assessment Tools for Occupational Ergonomics - page 969

50
The ACGIH TLV w for
Low Back Risk

50.1 Overview ................................. 50-1
50.2 TLV Development Background . . .............. 50-2
Spine Load Estimates † Load Tolerance † Studies of Lift
Location † Repetition Modifiers
50.3 Using the Lifting TLV . ...................... 50-7
About the Lifting TLV † Instructions for Determining the
Lifting TLV † If a Lifting Task Exceeds the
TLV † Example 1 † Example 2

William S. Marras
The Ohio State University
Chris Hamrick
Ohio Bureau of Worker's
Compensation

50.1 Overview

The Lifting TLV (threshold limit value) was the product of a team of scientists whose goal was to develop
a lifting guideline that was accurate, used the latest scientific information, and easy to use. This group of
scientists consisted of Lawrence J. Fine, Christopher Hamrick, W. Monroe Keyserling, William S. Marras,
Robert Norman, Barbara Silverstein, and Thomas Waters with correspondence members consisting of
Peter Buckle and John W. Frank. The product of this group's work has been presented as an ACGIH
2005 TLV. This chapter is based upon the work of the committee establishing this NIE (notice of
intent to establish) of which the two authors of this chapter were members.
The scientific rationale for this TLV is based on the most recent biomechanical, psychophysical, and
epidemiological studies, which together demonstrated a causal association between lifting activities
and increase risk of low back disorders characterized by pain and the temporary or prolonged inability
to perform normal occupational and nonoccupational activities. The model for the structure of this TLV
was based upon the structure of the Finnish lifting guidelines and the 1995 Occupational Safety and
Health Administration (OSHA) draft standard. These approaches were latter incorporated in the State
of Washington Ergonomic Rule. The approach for these efforts was to define the vertical and horizontal
space relative to the base of the spine (L5

S1) of the material handler. Surveillance studies have shown
that the single strongest indicator of risk for a lifting task was the load moment (weight of the object lifted
times the distance from the spine) relative to L5

/

S1 (Marras et al., 1993). In addition, biomechanical
studies have indicated that the vertical location of a load relative spine has profound biomechanical
implications for spine loading and tolerance (Marras, Granata, Davis, Allread & Jorgensen, 1999). There-
fore, a tool that identifies the origin location of the load to be lifted from a horizontal and vertical
location perspective was a reasonable approach.
Lift origins were divided into 12 horizontal and vertical zones relative within the sagittal plane of the
body (Table 50.1). The lift height zones consisted of four regions: (1) the region from 30 cm above to
8 cm below shoulder height (reach limit), (2) knuckle height to below shoulder height, (3) middle shin
height to knuckle height, and (4) floor to middle shin height. Horizontal location origins were divided

/

50-1