Handbook of Solvents - George Wypych - ChemTech - Ventech!

20.5 Lymphohematopoietic study of workers exposed to benzene 1371
we now know is extremely and significantly higher than the standard allowed today from a
regulatory point of view. At the request of the petrochemical companies, the authors decided
to reevaluate the content of benzene in solvents and for this purpose a total of 8 samples
of low boiling petroleum naphtha were obtained. After utilizing methodology which
included, among others, mass spectrometry for benzene content, the authors concluded
that, in general, the benzene content of solvents ranged from 1% to 4% in volume. They
have further shown that in the air of one plant where hexane with a relatively low benzene
content (1.5%) was used as a solvent in a fabric-spreading operation, a benzene vapor concentration
of 1 ppm was found. Since exposure to benzene is cumulative, if a worker is exposed
to hexane containing 1.5% benzene, with both inhalation and skin contact, the
cumulative exposure over a certain period of time increases the risk of developing benzene
related cancers as described by the Rinsky model. The study by Pagnotto, 66 looked at and
analyzed 32 naphtha solvents. The benzene concentration ranged from 1.5% to 9.3% by
weight. Excessive benzene exposure was found at 3 out of 4 plants during their operations
on a daily basis. On one occasion the concentration of benzene vapor was as high as 125
ppm (extremely high), and the urinary phenol excretion of the workers in these 3 plants
were the highest that these investigators report ranging from 370 to 917 mg per liter of urine.
These study indicate that solvents which contain benzene, even at levels of 1.5% per volume,
can be associated with significant atmospheric exposure to benzene, shown as causing
human exposure with significant excretion of phenol in the urine indicative of heavy benzene
exposure. The investigators recommended additional ventilation, and on a follow-up
visit the benzene exposure was found to have been reduced to about 70 ppm with urinary
phenols of less than 70 mg per liter, still significantly elevated and considered a significant
risk. These investigators also looked at blood examinations of 47 men at these plants. Five
employees showed lower hemoglobin. One man showed a low hemoglobin at the age of 28,
having been employed for 3 years in the environment preparing mixes for the saturating machine.
While leukemia was suspected due to bone marrow disease, the patient was treated
with iron and recovered. The authors conclude that excessive benzene exposures is consistently
found on saturators using naphtha containing more than 3% benzene. This study further
shows the importance of assessing benzene concentration is other solvents, from a
dosimetry point of view.
The manuscript entitled A Recommended Standard for Occupational Exposure to Refined
Petroleum Solvents from the U.S. Department of Health, Education and Welfare, Public
Health Service, Center for Disease Control, National Institute for Occupational Safety
and Health, July 1977, 67 recommended standards to be applied to occupational exposure of
workers to the following refinery petroleum solvents: petroleum ether, rubber solvent, varnish
maker’s and painter’s naphtha, mineral spirits, Stoddard solvents, and kerosene are all
included in the term refined petroleum solvents. According to these standards petroleum
ether and rubber solvents which contain 1.5% benzene, varnish maker’s and painter’s
naphtha which contain 1.5% benzene, mineral spirits which contain 13-19% aromatics,
Stoddard solvent which contains 0.1% benzene, 140 Flash Aliphatic Solvent which contains
0.7% benzene, kerosene. NIOSH indicated that some of the refined petroleum solvents
contain aromatic hydrocarbons including, in some cases, benzene. Standards were applied,
among others, to reduce the benzene exposure. Among others, the use of respirators and
skin protective devices were required to protect from the effects of the solvents, as well as
the benzene component. 67 In his testimony in front of the Occupational Safety and Health