Handbook of Solvents - George Wypych - ChemTech - Ventech!

1372 Nachman Brautbar
Administration, 68 Proctor testified that, among others, refining operations are continuously
changing. Many refineries obtain crude of differing characteristics from various producing
areas which sometimes must be processed individually due to crude incompatibility and
produce requirements. This means the operation of a crude fractionation unit is altered frequently;
a single crude run may be as short as 2 days. Consequently, the crude tankage,
crude fractionation units, and all downstream processing units frequently contain benzene.
Proctor further stated that it should be clear by now that benzene is a naturally occurring
compound in crude oil and is also found in the catalytic and cracking process, and therefore
will always be a contaminant of these solvents. Benzene levels in gasoline today are running
about 1.1% on the average across the nation but occasionally may reach 4% on individual
samples. Reduction of benzene levels in gasoline is technically possible through employment
of a number of physical processing schemes to the various gasoline component
streams. He further testified that any attempt of physical separation of hydrocarbons, such
as distillation, solvent extraction, or adsorption, the separation is not 100% complete.
Therefore, some residuals of benzene will always be present in the remaining fraction.
Therefore he recommended that benzene should be converted to cyclohexane by hydrogenation
which would require an expensive catalyst, expensive high pressure reaction vessels,
and consumption of valuable hydrogen. The testimony further indicates that it is believed
that it is almost physically impossible to reduce these streams below 0.1% benzene. The
1978 OSHA 69 indicate that “The record establishes that there is a wide variation in the benzene
content of petroleum solvents used in the rubber, paints, coatings, adhesives, sealants,
and other downstream industries. As reported by Smith, reporting on behalf of MCA, 69 the
benzene content of petroleum solvents of all types generally range from under 0.1% to 4%.
Data submitted by downstream industries confirms that benzene is present in virtually all
petroleum solvents, at levels which approach and even exceed 3.5% in some cases.” It was
stated that in the rubber industry, solvent benzene content appears to range from 0.1% to
0.7% or slightly higher. Similarly, solvents used by adhesive manufacturers show broad
variations from less than 0.1% to 3.5%. 69 Representatives of the paint industry report variations
from under 0.1% to as high as 3.7%. 69 Smith in his testimony emphasized that solvent
benzene content is likely to vary substantially among supplies, among different plants of the
same supplier, and among deliveries from the same plant. Because refinery processes are
not designed to precisely control benzene content, variations will inevitably occur.
These data clearly show that benzene contents in solvents are difficult to control and
vary depending on the sources, processes and therefore solvent exposure must take into account
the level of benzene concentration in these solvents. These data, taken together with
the most recent study of Brenner et al. 6 show that industrial toluene solvent does contain
benzene and contributed significantly to the exposure via the skin to benzene. One must remember
the importance of benzene exposure through the use of solvents produced through
the petrochemical refining processes.
20.5.10 GENETIC FINGERPRINT THEORY
Benzene and its metabolites have long been known to cause chromosomal aberrations of
various types of cell cultures of exposed humans. (To be discussed in Chapter 20.6 in this
book entitled as Benzene Exposure and Sister Chromatoid Changes.) While it is true that
genetic changes have been described and frequently effect chromosomes 5 and 7, and others,
there is no scientific evidence that these are required for the diagnosis of benzene exposure
related cancers. Specifically, many cases of patients who have been exposed to