PARAMETER NON-OILWORKERS (N=30)   Range  Mean ± SD OIL WORKERS (N=303) Range Mean ±SD P-Value(2-tailed) Normal range & Unit of parameter
AGE 35.00-59.00 47.37 ± 6.74 28.00-60.00 43.30 ± 7.03 0.003  
SERVICE PERIOD** 3.00-34.00 20.03 ± 8.77 3.00-34.00 16.18 ± 6.42      0.003 Up to 35Yrs
ESR 1.00-36.00 6.60 ± 7.81 1.00-100.00 10.94 ± 11.82 0.05 0-7mm/hr (M), 0-10mm/hr (F)
Hb 9.10-14.90 13.01 ± 1.54 7.60-21.10 13.19 ± 1.31 0.487 13-18g/dl (M), 12-15g/dl (F)
PCV 30.00-49.00 42.70 ± 5.01 25.00-58.00 43.31 ± 4.09 0.448 40-50%(M), 36-47%(F)
PLATELETS × 109 141.00-382.00 239.23 ±57.30 75.00-430.00 232.41± 63.18 0.570 150-400 ×109 /L
TOTAL WBC   × 109 4.90-11.00 7.36 ± 1.64 3.20-86.00 7.07 ± 6.61 0.813 4.0-11.0 ×109 /L
LYMPHOCYTE 25.00-57.00 41.60 ± 10.16 18.00-75.00 52.28 ± 9.25 0.000  
GRANULOCYTE 43.00-75.00 58.40 ± 10.16 25.00-82.00 47.72 ± 9.24 0.000  
T-test was the statistical tool applied. *Indicates statistically significant difference [** Service Period = number of years the worker had been engaged in the work, amounting to his/her cumulative years of exposure to the hazards of his/her workplace (i.e. exposure period). Presently, 35yrs is the maximum service period that qualifies an average civil servant for retirement in Nigeria, and is therefore considered as the upper limit of normal for service period in this report]                                                                                                                                     Key for letters in Normal Range: M = Males., F = Females. 
Table 1: Value ranges and means of haematological parameters studied in the oil workers (PPMC and PHRC put together) compared with the non-oil workers.