Risk of cancer in an occupationally exposed cohort with increased level of chromosomal aberrations.

We used cytogenetic analysis to carry out a cohort study in which the major objective was to test the association between frequency of chromosomal aberrations and subsequent risk of cancer. In spite of the extensive use of the cytogenetic analysis of human peripheral blood lymphocytes in biomonitoring of exposure to various mutagens and carcinogens on an ecologic level, the long-term effects of an increased frequency of chromosomal aberrations in individuals are still uncertain. Few epidemiologic studies have addressed this issue, and a moderate risk of cancer in individuals with an elevated frequency of chromosomal aberrations has been observed. In the present study, we analyzed data on 8,962 cytogenetic tests and 3,973 subjects. We found a significant and strong association between the frequency of chromosomal aberrations and cancer incidence in a group of miners exposed to radon, where a 1% increase in frequency of chromosomal aberrations was followed by a 64% increase in risk of cancer (p < 0.000). In contrast, the collected data are inadequate for a critical evaluation of the association with exposure to other chemicals.

Chromosomal abnormalities in soft coal open-cast mining workers.

Chromosome aberration tests on cultured peripheral blood lymphocytes were carried out in two groups of open-cast mining workers engaged in stripping operations (Group I) and digging operations (Group II), in a group of coal cleaning plant workers used as a positive control, and in a group of nonexposed subjects serving as matching controls. Peripheral blood samples in group I and group II miners were collected in March and June of 1984, the antimutagenic potential of long-term prophylactic vitamin administrations (1 g of ascorbic acid given daily for a period of 3 months and 100 mg of vitamin A a day for two 5-day cycles) initiated after the first blood sampling was tested in group II miners. The frequency of aberrant cells (% AB.C.) found in the cultured lymphocytes of group I miners was increased at both times of measurement (2.41% AB.C. and 2.29% AB.C.), in group II miners given the vitamin prophylaxis it dropped significantly (P greater than 0.01) from the initial 3.16% AB.C. in March to 1.77% AB.C. in June, and in the group of coal cleaning plant workers (1.30% AB.C.) it was more or less equal to that of matching controls (1.21% AB.C.). Implicitly, coal dust alone can hardly be made responsible for the rise in % AB.C. It appears that the increase in frequency of chromosome aberrations observed in soft coal open-cast mining workers rather reflects an increased risk of genetic injury due to exposure to ever-present fumes and fire hazards that may give rise to the mutagenic chemicals belonging to a class of polycyclic aromatic hydrocarbons. The antimutagenic effect of ascorbic acid prophylaxis was characterized by a significant drop in % AB.C. and a speed-up of the lymphocyte cell cycle expressed as the proliferating rate index (PRI) whose value rose from the original 1.41 to 1.69, thus reaching the PRI value of matching controls (1.63).

Cytogenetic analysis of peripheral blood lymphocytes in glass workers occupationally exposed to mineral oils.

Chromosome aberration tests were carried out in a group of 31 pressed glass makers operating an automatic line of press-and-blow machines known to release mineral oil mists containing relatively high concentrations of the mutagenic chemicals belonging to a class of polycyclic aromatic hydrocarbons (PAH). The workers were exposed to the mineral oil aerosol levels that did not exceed the Czechoslovak maximum allowable concentration limit of 5 mg . m-1 of air. The tests revealed that the frequency of aberrant cells (% AB.C.) and the value of breaks per cell (B/C) ratio found in mineral oil-exposed workers were increased significantly, accounting for 4.65 +/- 0.29% AB.C. (0.0532 B/C) vs. 1.13 +/- 0.19% AB.C. (0.0113 B/C) seen in matching controls. Also, a higher rate of dicentrics, reciprocal translocations and cells with pulverization was observed in this group of glass workers. These finding are considered as evidence suggesting that these workers might experience an increased risk of genetic injury due to exposure to mineral oil mists.

High-dose ascorbic acid prophylaxis in workers occupationally exposed to halogenated ethers.

A possible prophylactic effect of ascorbic acid (AA) was studied in a group of 77 workers occupationally exposed to carcinogens bis(chloromethyl) ether and chloromethyl methyl ether. The effect of prophylactic treatment was assessed by cytogenetic analysis of chromosome aberrations, and by determination of blastic transformation and mitotic index in peripheral lymphocytes. Blood samples were taken at the beginning and at the end of 5-month AA prophylaxis. Simultaneously synthetic resin workers and subjects without any occupational exposure were used as controls. Administration of AA in daily doses of 1 g, 5 days per week, significantly decreased the frequency of aberrant cells (AB.C.) from 3.73% to 2.13%, and increased % of blastic transformation (BT) from 59.15 to 67.26 and of mitotic index (MI) value from 1.04 to 1.42. The respective data in synthetic resin workers were 3.65 against 3.52% of AB.C., 55.82 against 63.73% of BT and 0.78 against 1.08 of MI, and in nonexposed subjects 1.64 against 1.88% of AB.C., 52.10 against 55.73% of BT and 1.07 against 1.14 of MI. Smoking habits had no clear-cut effect on detected changes. These study results have confirmed that the risk of genetic injury, if assessed by the frequency of chromosome aberrations in peripheral lymphocytes, was considerably reduced after AA prophylaxis in workers occupationally exposed to halogenated ethers.