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. Brit. J. industr. Med., 28, 296-302. Haematological effects of chronic benzene poisoning in 217 workers. A haematological study consisting of the determination of RBC, WBC, PCV, platelets, and differential counts was carried out, together with bone marrow puncture and haemoglobin analyses in appropriate cases, on a control population of 100 normal people and on 217 male labourers, 95% of whom worked with solvents containing benzene in small shops manufacturing shoes under unhygienic conditions. The concentration of benzene in the workplaces ranged between 30 and 210 p.p.m., and the period of exposure between 3 months and 17 years.In 51 of the 217 workers (23 50%) haematological abnormalities attributable to chronic benzene poisoning were detected. Thus, leucopenia was present in 9 70 %, thrombocytopenia in 1-84%, leucopenia associated with thrombocytopenia in 4-6%, pancytopenia in 2-76%, acquired pseudo-Pelger-Huet anomaly in 0-46%, lymphocytosis in 0-46 %, giant platelets in 0-46%, eosinophilia in 2-30%, basophilia in 0-46%, and eosinophilia associated with basophilia in 0*46% (the maximum normal levels for eosinophils and basophils were 8% and 2 % respectively).Acquired pseudo-Pelger-Huet anomaly was detected in a worker with heterozygous betathalassaemia (HbA2 4-1 % and HbF 8-7%) in whom the only effect of benzene was on the leucocyte nuclei, all other haematological values being within normal limits. On the other hand, in 33-1 % of the workers the haemoglobin was less than 12 g/100 ml and in 32-7% the PCV was less than 40 % with the MCV ranging between 86 and 96 ,um3. In none of them did MCV exceed 100 ,um3. Thirty-on-per cent. of these anaemic workers were treated with adequate doses of oral iron, which resulted, in all cases, in a complete disappearance of the anaemia. Therefore, it is difficult to attribute this anaemia to the effect of benzene alone.Thus it is concluded that benzene exerts its harmful effect, primarily on the leucocytes, with eosinophilia and basophilia as inconstant findings, secondarily on the platelets causing thrombocytopenia, and finally on all three series giving rise to pancytopenia.

The distribution of various types of leukemia due to chronic exposure to benzene is described in a series comprising 34 cases. The incidence of leukemia among 31 shoe-workers was 13.5/100,000. Acute myeloblastic leukemia was the most frequent type, followed by preleukemia, acute erythroleukemia and acute lymphoblastic leukemia. The extreme rarity of chronic myeloid leukemia was a noteworthy finding. The differences and similarities between the distribution of various types of leukemia in different series of patients with chronic exposure to benzene and ionizing radiation are discussed.

From 1967 to September 1973, 26 patients with acute leukemia or preleukemia were seen in Istanbul among 28,500 shoeworkers exposed chronically to benzene. The incidence of leukemia among these workers was 13/100,000, which is a marked and statistically significant increase over that for leukemia in the general population and provides cogent evidence for the clinical impression of a leukemogenic effect of benzene in man.

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