|BACKGROUND: Oxygen is essential for life. If any factor inhibits the body's usage of oxygen, the body will react with a variety of feedback systems to retain life. When a person stays in an area with a slightly lower oxygen concentration for a long period, his body will react with an increase in the amount of erythrocytes (Cuyton & Hall, 2000:497). When a group of people shows an increased amount of erythrocytes when compared to a normal group, it could be that the first group's bodies have reacted to an insufficient oxygen supply to the tissues. The purpose of this study is to investigate if workers at a coal tar plant have disturbed haematological values and should that be the case, if, it is caused by volatile organic compounds. METHOD: A group of 20 white males working at a coal tar plant of a petrochemical factory was used as Experimental group. A control group of 20 white males living in a town which is remote from any petrochemical factory and which is on the same height above sea level as the Experimental environment, was paired to the Experimental group. Pairing of subjects was done on grounds of age, smoking habits, drinking habits, exercising habits, the period the person stayed in the area and usage of vitamin and iron supplements. Complete blood counts (CBC) of both groups were done, where the previous year's CBC results of the Experimental group were also gathered. Exposure of the Experimental group to volatile organic compounds (VOC) was monitored by using G.A.B.I.E. badges during the annual shut down of the factory. Oxygen, carbon dioxide and carbon monoxide concentrations were determined in both environments. The meteorological data of the Experimental environment were gathered on the days of VOC monitoring. RESULTS: The mean haematological parameters - from the CBC - of the Control group were normal. The Experimental group showed highly significant (p ≤ 0,001) differences in red blood cell count (RBC), haemoglobin (Hb) and haematocrit (Hct) when compared to the Control group, where the values of the Experimental group were higher than that of the Control group. The mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) of the Experimental group diminished significantly (p ≤ 0,05) over a period of one year. The Experimental group was exposed to 14 different VOC's and all the exposure levels were far below the exposure limits from the Hazardous Chemical Substances Regulations (1995) in the Occupational Health and Safety Act (85/1993). • Exposure to n-hexane and toluene showed strong negative correlations with the RBC. • Xylene showed a negative correlation with the MCV and a positive correlation with the MCH. • 3-methylpentane showed a positive correlation with the RBC. The oxygen, carbon dioxide and carbon monoxide concentrations of both environments were well below the prescribed limits. DISCUSSION: The Control group represented a normal group which means it can be proved that the Experimental group showed haematological disturbances because their RBC, Hct and Hb values were significantly higher than those of the Control group. When these disturbances were connected to the exposure to VOC's, correlations showed that VOC's had a close connection with RBC. A number of VOC's, like benzene, is known for its ability to cause damage to the bone marrow and to cause hyperplasia. Considering that the oxygen, carbon dioxide and carbon monoxide
concentrations were the same in both environments, and that height above sea level, habits and personal information with the Control group were compensated for, it seems as if a number of VOC's act synergistically to damage the bone marrow of the Experimental group. The body tries to compensate by producing more erythrocytes (Guyton & Hall, 2000:385) which is the cause of the high RBC, Hct and Hb. CONCLUSION: Workers of the Coal tar plant showed an elevated RBC, Hct and Hb. Exposure to a variety of VOC's could possibly cause destruction of the bone marrow which in turn caused hyperplasia of the remaining bone marrow, thereby attempting to supply the demand for red blood cells in the body and thereby causing the red blood cell count to raise. Although the exposure to VOC's complies entirely to the law, the effect of long-term low level exposure may be the cause of the disturbed erythrocyte parameters. The lowering of MCV, MCH and MCHC of workers is probably an indication that a type of anaemia is beginning to develop. But further research is necessary before any definite utterance can be made.
Research concerning the erythropoietin levels, leukocytes, platelets and bone marrow function of these workers should be conducted. A longitudinal study where animals are used as experimental subjects should throw some light on the subject.