OCCUPATIONAL EXPOSURE OF AUTOMOBILE MECHANICS TO PETROLEUM PRODUCTS

We carried out a  research  to investigate the potential risk of exposure to petroleum fumes among automobile mechanics in Lagos, Nigeria. Structured questionnaire was administered to elicit information on their exposure to petroleum products.  Automobile mechanics in their line of occupation are constantly exposed to petroleum products. These products contain toxic compounds such as Benzene, Toluene, Ethyl benzene and Xylene, (BTEX). Venous blood was taken from exposed subjects for Methaemoglobin (MetHb), Packed Cell Volume (PCV), haemoglobin and BTEX.

One of the effects of benzene in the body is the production of methaemoglobin (MetHb) which differs from haemoglobin. Haemoglobin accepts and transports oxygen only when the iron atom is in its ferrous form. When haemoglobin becomes oxidized, iron is converted to the ferric state (Fe3+) or MetHb. Methemoglobin cannot bind oxygen, MetHb lacks the electron that is needed to form a bond with oxygen and, thus, is incapable of oxygen transport.  

Our results reveal that the mean methaemoglobin value in the blood of the automobile mechanics (3.68%-7.33%) were significantly higher (p<0.05) than the control subjects (0.83%). MetHb level was directly proportional  to the duration of exposure with 0-5 years exposure having (0.4%) and 21-30 years of exposure having (13%).  We discovered that mechanics with many years of exposure has high MetHB in their blood. Since red blood cells are continuously exposed to various oxidant stresses, blood normally contains MetHb levels of between 1and 3% . Considering that MetHb has little affinity for oxygen, transport of the later to cells is hindered resulting in functional anaemia . As the level of MetHb increases, symptoms like shortness of breath, palpitation, anxiety and confusion occur . Humans are commonly exposed to benzene and other VOCs through the pulmonary and dermal pathways.

Methemoglobin saturation is expressed as the percentage of hemoglobin in the methemoglobin state; That is MetHb as a proportion of Hb.

·         1-2% Normal

·         Less than 10% metHb - No symptoms

·         10-20% metHb - Skin discoloration only (most notably on mucous membranes)

·         20-30% metHb - Anxiety, headache, dyspnea on exertion

·         30-50% metHb - Fatigue, confusion, dizziness, tachypnea, palpitations

·         50-70% metHb - Coma, seizures, arrhythmias, acidosis

·         Greater than 70% metHb - Death

Our study has established a strong evidence between increased exposure to petrol fumes among automobile mechanics and level of MetHb.   The awareness of effects of exposure to petroleum fumes and use of personal protective equipment by automobile mechanics to reduce exposure to petroleum products in their workshops is highly recommended.