Case Study
Skin absorption of isocyanates: Use of MDI adhesive
The Problem
During the manufacture of industrial flooring, chipboard panels
were coated with isocyanate-based adhesive (MDI, methyl diphenyl
diisocyanate) before metal facing plates were manually attached to
either side. The panel was then mechanically crimped prior to
be taken manually off the production line for storage. The
workers were wearing leather gloves, primarily for protection
against physical injury during the manual tasks. Urine
samples showed that body burdens for MDI substantially exceeded the
UK guidance value in a number of workers.
What We Did
We looked at the correlation between airborne MDI and levels
found in urine. This showed that the urine samples indicated
substantially more MDI exposure than expected from the measured air
levels.
In light of this, and the nature of the handling tasks within
the process, we suspected that skin exposure could be contributing
to the overall body burden. The glove regime was reviewed and
it was decided to replace the leather gloves with polyester gloves
with a polyurethane palm. These would provide chemical
protection and, being cheaper, could be changed more
frequently.

Outcome/Benefits
Following the intervention, body burdens were significantly
reduced, with all workers tested showing lower levels in
urine. Whereas three-quarters of the workers exceeded the
biological monitoring guidance value before the intervention, only
a quarter still exceeded it (marginally) afterwards. The
airborne levels of MDI remained similar after the intervention,
indicating that dermal contact had been the primary source of
exposure.
A straightforward improvement in the glove regime markedly
reduced worker exposure to a potent skin and respiratory sensitiser
thus reducing the likelihood of future ill-health.
With thanks to Aspen
Environmental
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