Handbook of Solvents - George Wypych - ChemTech - Ventech!

1370 Nachman Brautbar
based on the work of others, that the major clone in chronic myelocytic leukemia affected
cells capable of becoming lymphocyte, granulocyte, and erythrocyte differentiations leading
to the conclusion that transformation events occur at an early multipotent stem cell
level.
Nilsson et al. 42 investigated Swedish seamen, 20-64 years of age, who had been exposed
to cargo vapors for at least 1 month on chemical or product tankers, had an increased
risk of lymphatic and hematopoietic malignancies odds ratio of 2.6 with 95% confidence interval,
with a significant exposure response relation. The odds ratio was increased for
non-Hodgkin’s lymphoma at 3.3 with 95% confidence interval and was statistically significant.
Rinsky et al. 43 studied a cohort of 11,065 white men with at least 1 ppm per day of cumulative
exposure to benzene. They have demonstrated that there was a statistical
significant increase in death from all lymphatic and hematopoietic neoplasms, 15 observed
versus 6.6 expected standard mortality ratio which is 227, 95% confidence interval, further
demonstrating that benzene is toxic to all cell types.
Hayes et al. 47 studied a cohort of 74,821 benzene exposed and 35,805 unexposed
workers from 1972 until 1987 in 12 cities in China. By and large this is the largest and most
significant cohort of benzene workers studied and published. The investigators found that
1) benzene exposure is associated with a spectrum of hematological neoplasms, 2) workers
with 10 or more years of benzene exposure had a risk ratio of developing non-Hodgkin’s
lymphoma of 4.2 with 95% confidence interval, and the development of this neoplasm was
linked most strongly to exposure that had occurred at least 10 years before the diagnosis,
and 3) the risk for the combination of acute non-lymphocytic leukemia and related
myelodysplastic syndromes was significantly increased among those with more recent benzene
exposure. These studies confirm the previous studies proving that the damage from
benzene is to all cell type.
Linet et al. 45 studied hematopoietic malignancies and related disorders among benzene
exposed workers in China and showed a wide range of hematopoietic malignancies. Yin et
al. 46 examined a large cohort of benzene workers and concluded that benzene exposed
workers have a statistically significant excess death due to leukemia, risk ratio of 2.3 with
95% confidence interval; malignant lymphoma, risk ratio of 4.5 with 95% confidence interval;
and non-neoplastic diseases of the blood.
In summary, these epidemiological studies published in the peer-reviewed scientific
literature and relied on by scientific and governmental agencies clearly show 1) significant
statistical association between benzene exposure and lymphohematopoietic cancers of all
cell types, 2) an increased risk and/or increased standard mortality rate over a factor of 2 in
patients exposed to benzene with the development of non-Hodgkin’s lymphoma,
leukemias, and other lymphohematopoietic malignancies, and 3) benzene is carcinogenic
with a linear dose response demonstrating no threshold.
20.5.9 SOLVENTS AND BENZENE
Solvents commonly used in the industry have been shown to contain benzene. Elkins, et
al. 65 found that from time to time analyzed solvents for benzene content showed anywhere
from 1% to 2% benzene. In that paper, which was published in 1956, the authors state that
the TLV value from a regulatory point of view, at that time, was 35 ppm compared with
100 ppm previously. According to their calculations, they found that a benzene content below
3.5% will be necessary, for instance in solvents containing naphtha, hexane, and toluene,
otherwise the permissible level for benzene vapor will be exceeded over 35 ppm, which