Handbook of Solvents - George Wypych - ChemTech - Ventech!

1258 Pentti Kalliokoski, Kai Savolainen
parts of the pressroom. 39 The mean exposure level of toluene can be less than 20 ppm in a
modern rotogravure printing plant. 37
As stated earlier, toxic alkoxyethanols and their acetates have been used commonly in
silkscreen printing inks. Those have no warning odor and are, therefore, easily considered
to be safe. Airborne concentrations of 2-ethoxyethanol and 2-ethoxyethyl acetate from 3 to
14 ppm (both have a TLV of 5 ppm, the Finnish OEL 2 ppm) have been detected during
printing. 40,41 Because the inhalation exposure consists only a part of the total exposure and
absorption through the skin is of equal or greater importance, biological monitoring is the
preferred exposure assessment method. The concentration of the toxic metabolite,
2-ethoxyacetic acid, in urine is the most commonly used method. Biomonitoring is also important
because, otherwise than most other solvents, 2-ethoxyacetic acid has a long half-life
and, therefore, it accumulates in the body during the workweek. Its ACGIH BEI is 100 mg/g
creatinine (109 mmol/mol creatinine). A lower value of 30 mmol/mol creatinine has been
proposed in Finland. 42 The average urinary 2-ethoxyacetic acid concentrations were found
to increase from 40 to near 90 mmol/mol of creatinine during a workweek. 42
Other alkoxyethanols, especially 2-methoxyethanol and 2-butoxyethanol and their acetates
have also been used in silkscreen printing inks. The TLV for 2-methoxyethanol and
its acetate is 5 ppm (their Finnish OEL is 0.5 ppm) and 25 ppm for 2-butoxyethanol (the
Finnish OEL is 20 ppm for 2-butoxyethanol and its acetate but a value of 5 ppm has been
proposed. 42 ACGIH has not set BEIs for these compounds. Limits of 3 mmol methoxyacetic
acid/mol creatinine and 60 mmol butoxyacetic acid/mol creatinine has been recommended
in Finland for the concentrations of the urinary metabolites. 41 Mean inhalation exposure
levels to 2-methoxyethyl acetate from 0.2 to 1.9 ppm have ben reported. 40,42 The urinary
methoxyacetic acid concentrations have ranged from 0.1 to 10.7 mmol/mol creatinine. 42
Airborne mean 2-butoxyethanol and 2-butoxyethylacetate concentrations from 0.1 to 3.2
ppm have been observed. 40,42
The use of safer alkoxypropanols and their acetates is rather new in silkscreen printing
inks. Among them, only 1-methoxy-2-propanol has a TLV (100 ppm). Its German MAK
value is 50 ppm (also given for its acetate). A German MAK value of 20 ppm have been set
for 2-methoxy-1-propanol and its acetate (this is also the Norwegian OEL). These have no
BEIs or official biological action limits in any country. A value of 3 mmol
2-methoxypropionic acid/mol creatinine has been found to correspond to inhalation exposure
to 1-methoxy-2-propyl acetate at the German MAK level. 42 The corresponding value
for 1-ethoxypropionic acid is 40 mmol/mol creatinine. 42 Even though alkoxypropanols are
less toxic than alkoxyethanols and their dermal uptakes are lower, they have the disadvantage
of having higher vapor pressures. However, if enclosed and automatic machines have
been used airborne levels of alkoxypropanols have remained well below the German MAK
levels. 42 Screen printing inks also contain other solvents, e.g., toluene, xylene, and
cyclohexanone (TLV 25 ppm with skin notation, the Finnish OEL 25 ppm as a ceiling value
and with skin notation).
The printers are also exposed to solvents while cleaning the press. The rollers are
cleaned regularly. Occasionally, ink stains are also removed from other parts of the presses
and floor (see 18.4.6).
18.4.6 DEGREASING, PRESS CLEANING AND PAINT REMOVAL
Chlorinated solvents have traditionally been used as metal degreasing agents. Trichloroethylene
(TLV 50 ppm; the Finnish OEL 30 ppm) and 1,1,1-trichloroethane (methyl chloro-