inhalation challenges to metal working fluids
Vicky Moore1, Alastair Robertson2
and Sherwood Burge1
Lung Disease Unit, Birmingham Heartlands Hospital, Birmingham, United
Kingdom, 2Department of Occupational Health, University Hospitals,
Birmingham, United Kingdom
Metal working fluid (MWF) is
recognised cause of occupational asthma and is becoming increasingly
prevalent. In Birmingham, UK there are a large number of industries
using metal working fluid to machine automotive and aircraft parts. The
oil in water emulsion can be used at varying ratios generally ranging
from 3% oil in water up to 10%.
20 workers underwent specific inhalation challenge (SIC) tests to metal
working fluid. Challenges were set up to mimic occupational exposures
using indirect (into the room) and direct (into breathing zone) methods
of nebulisation of new and used MWF. Exposures lasted from 5 minutes up
to 70 minutes in total (spread over 3 exposures). Workers were also
exposed to metal contaminants of the MWF by nebulisation of cobalt
chloride (cobalt exposure can be from carbide tips used for machining)
and potassium dichromate (chrome exposure can be from the machining of
Overall, 15 workers had positive SIC tests to either MWF or metal
contaminants (cobalt/chrome). The Venn diagram in Figure 1 shows the
results. 8 workers had a ≥2 fold change in methacholine
reactivity between pre and post challenge.
inhalation challenge tests to MWF did not produce non-specific
reactions. Contaminants of the MWF can be the cause of occupational
asthma even with a negative challenge to used MWF.
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