Handbook of Solvents - George Wypych - ChemTech - Ventech!

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quite complicated, and if biological monitoring methods are available those usually provide
a more practical alternative.
Urine and blood are the most commonly used biological samples. Exhaled air samples
can also be used. Sampling is usually carried out at the end of the shift. Because the amount
of water consumed affects the concentration of the solvent or its metabolite in urine,
creatinine (a normal constituent of urine) correction is often applied (mass analyzed is presented
per gram of creatinine). Alternatively, the correction can be made for the relative
density of urine. A density of urine of 1.024 is usually applied for this purpose. In principle,
collection of 24-hour urine would be an ideal approach for biological monitoring because
then the actually excreted amount of the metabolite would be measured. Because this is very
difficult to carry out creatinine or density correction is generally chosen as a more practical
alternative. Unfortunately, not only several ways of correction for the density of urine are
being used but also several different units have been adopted. For example, the ACGIH
BEIs are usually given as mg/g creatinine but the values of the FIOH and many other European
organizations are presented as μmol/l of urine. In addition, other units, such as
μmol/mol of creatinine, are used. The mass units given in mg can be converted to mmol by
dividing by the molecular weight of the compound (molecular weight of creatinine is 113).
On the other hand, because the concentration of creatinine in urine varies and it is determined
separately for each individual sample, values given with and without creatinine correction
(or density correction) cannot be compared directly. That is the reason why the BEIs
given by different institutions or agencies have not been converted to the same units in the
text. As a rule of thumb, the concentration per gram of creatinine can be obtained by multiplying
the concentration per liter of urine with a factor of 0.5 - 1.0.
Airborne solvent concentrations usually vary much with time. Although repeated random
personal sampling is theoretically the optimal method for inhalation exposure assessment,
it is very time-consuming and does not necessarily reveal the reasons for exposure.
Often, occupational hygiene surveys are conducted only to make certain that the concentrations
of air impurities are in compliance with the OELs. Also, the European standard (EN
689/95) for occupational exposure assessment is primarily issued for this purpose. It would,
however, be practical if the measurements conducted would also provide useful information
for planning of remedial measures if the measurements reveal those to be necessary.
For this purpose, it is important to recognize the difference between manual tasks and process
industries.
In manual tasks, emissions are released very close to the worker. Most problematic
solvent exposures occur while performing manual tasks, such as painting, gluing,
degreasing, and cleaning. Batch processes in paint and printing ink manufacture also contain
many manual tasks. Manual lay-up methods are common in the reinforced plastics industry.
The workers often perform different tasks with different exposure levels. All major
tasks should be investigated under various conditions. Smoke tube tests provide useful information
on the spreading of solvent vapor and the efficiency of local exhausts. Good enclosure
for the emission source is important for successful exposure control. Detailed
instructions for ventilation arrangements in various industries are available (references will
be given later).
Rotogravure printing is an example of a process industry with solvent exposures. The
process is, in principle, closed but emissions take place from the openings for the paper web.
The workers do not need to stay in the immediate vicinity of the emission sources but can