Assessing the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV): lifting beyond 30 degrees torso asymmetry

Abstract

Dynamic lifting jobs result in a risk of low back disorders (LBDs) higher than any other industrial jobs. There are several ergonomics lifting assessment methods used to evaluate OLBD risk in the lifting jobs. The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) lifting assessment method is one of the assessment tools used to assess the lifting jobs. The ACGIH TLV tool considers factors such as; the vertical height of the lift, horizontal location of the lift, lift frequency and duration, and the load weight. There is a void on ACGIH TLV, in which it does not apply on lifting jobs that involve torso asymmetry greater than 30?, and the professional judgment is required to suggest the right TLV in such cases. The objectives of this study are to a) determine the OLBD risk values for lifting jobs that involve torso asymmetry less than 30? (i.e. 0, 15, and 30?) and greater than 30? (i.e. 45, 60, 75, and 90?) and b) adjust the TLV's for lifting jobs with OLBD Risk probability greater than 30% (i.e. moderate risk). Twenty male college students were included in this lifting experiment. The lifting zones in this study were according to the ACGIH TLV third lifting table. The lumbar motion monitor (LMM) device and the Ballet 2.0 software that comes along with the LMM were utilized to collect and analyze the torso kinematics. The software provided OLBD Risk probability value for each lifting task. The results have shown that the greater the torso asymmetry angle, the higher the OLBD Risk value. Lifting jobs with torso asymmetry greater than 30? were in the moderate risk category in all lifting zones. Also, lifting jobs with torso asymmetry within 30? were in the moderate risk category only at mid-shin to knuckle zone in both horizontal distances. However, they were in the low risk category only in knuckle to shoulder zone in both horizontal distances. New TLV's were suggested for lifting jobs with a moderate risk of OLBD.