The ACGIH TLV for Low Back Risk - Fundamentals and Assessment Tools for Occupational Ergonomics - page 979

TABLE 50.4 TLVs for Lifting Tasks 2 h per day with 60 Lifts per hour or . 2 h per day with 12 Lifts per hour

Horizontal Location of Lift

Close Lifts: Origin
,

Intermediate Lifts:
Origin 30-60 cm
from Midpoint
between Inner
Ankle Bones

Extended Lifts: Origin
. 30 cm from

Midpoint between
Inner Ankle
Bones

60 to 80 cm from
Midpoint between
Inner Ankle
Bones a Lifting Height Zone

Reach limit b from 30 cm above
to 8 cm below shoulder height

16 kg 7 kg No known safe limit for

repetitive lifing c

Knuckle height d to below shoulder 32 kg 16 kg 9 kg

Middle shin height to knuckle height d 18 kg 14 kg 7 kg

Floor to middle shin height 14 kg No known safe limit

for repetitive lifing c

No known safe limit
for repetitive lifing c

a Lifting tasks should not be started at a horizontal reach distance more than 80 cm from the midpoint between the inner
angle bones (Figure 50.2)
b Routine lifting tasks should not be conducted from starting heights greater than 30 cm above the shoulder or more than
180 cm above floor level (Figure 50.2)
c Routine lifting tasks should not be performed for shaded table entries marked “No known safe limit for repetitive lifting.”
While the available evidence does not permit identification of safe weight limits in the shaded regions, professional judgment
may be used to determine if infrequent lifts of lifht weights may be safe.
d Anatomical landmark for knuckle height assumes the worker is standing erect with arms hanging at the side.
Source: Reprinted from ACGIH, 2004 Threshold Limit Values for Chemical Substance and Physical Agents & Biological
Exposure Indices, 2004. Cincinnati, OH: ACGIH. With permission.

The company redesigned the lifting task by installing a manipulator attached to an overhead
crane so that the shell could be lifted mechanically, thereby nearly eliminating the muscular
effort required by the machine operator (Figure 50.5). By reducing the muscular effort, the mechanical
stress on the spine is also reduced, thereby substantially reducing the risk of injury to the machine
operator.
In the year prior to installing the manipulator, the company reported nine injuries associated
with this task: two back sprains, six neck sprains, and one wrist sprain. In the year after the change,
no injuries have been reported to the population performing this task. The company also indicated
that productivity has increased by nearly 70%, and scrap rate has decreased from 2 to 0.8%.
As these examples illustrate, the Lifting TLV is a practical, easy to use tool that can be used in the
workplace to assess risk. The results can also be used to determine jobs which are candidates for redesign
and as an assessment tool after making job modifications to determine if the risk of injury has been
reduced to acceptable levels.

FIGURE 50.4 Lifting shell to press.