h.4Occupational exposure to MMT

h.4Occupational exposure to MMT

MMT is imported in bulk as a 62% solution in a mixed hydrocarbon solvent (HiTEC 3062) in isotanks of 10,000L capacity and transported by road or rail to several fuel refineries for addition to fuel. MMT is also imported in 205L steel drums and less commonly in 450 L CYL-type steel cylinders as 60% or 62% solutions and transported by road or rail to a small number of third party formulators for blending and packaging into aftermarket fuel additives. Most of the blending and packaging is conducted by two formulators. MMT is also imported in preformulated, prepackaged fuel additives and with locally formulated fuel additives and bulk LRP are distributed to numerous petrol stations and retail outlets.

h.4.1Bulk fuel and fuel additive blending at refineries and formulators

At refineries, isotainers are positioned by crane in a bunded area. A flexible hose is then connected manually to the lower delivery flange of the isotank through which the MMT solution is metered directly to the blending manifold at the designated LRP finished product tank or firstly pumped to a storage tank prior to metering to the LRP finished product tank. To facilitate emptying, the isotank is pressurised with nitrogen. All pumping and metering of the MMT solution in the fuel blending operation are conducted under automatic control in enclosed transfer systems. Bulk LRP containing MMT is then pumped from the finished product tank via enclosed lines to terminals or directly to road tankers.

At the refinery or terminals, blended LRP containing MMT at < 0.01% is pumped to road tankers for transport to petrol retailers. Transfer involves a manual connection and disconnection of a flexible transfer line between the LRP finished product tank or terminal manifold and lower fill port of the road tanker.

A total of 10-20 personnel are involved in the import, storage and blending of the MMT solution. At each site, fewer than 5 personnel are involved directly in the unloading of the MMT solution from isotanks and these are engaged in these operations typically for 10 -15 minutes, 4 times per year.

At third party formulators, drums or cylinders of MMT concentrate are typically opened in bunded areas and emptied by manually connecting a flexible hose to the dip leg located at the top of the cylinder or manually inserting a spear through a bung at the top of the 205 L drum. Cylinders may be pressurised with nitrogen to facilitate emptying. MMT is then pumped to a closed mixing vessel or to storage. After emptying drums and cylinders, residual MMT is captured typically by adding petroleum diluent by pump, manually swirling the containers and pumping the residue to the mixing vessel. After mixing, the formulated fuel additive containing MMT at < 10% w/w is gravity fed to and packed in sealed plastic bottles of up to 500 mL capacity.

Typically at each formulator, up to 3 warehouse personnel and up to 3 blending and 3 filling personnel handle imported MMT solutions in imported drums, cylinders or filled end-use plastic bottles. Blending activities typically occur for 2 - 8 hours/day for 2 –12 days/year. Filling/packing activities may occur for up 15 hours/day for 2 days/year.

Quality analysis personnel test blended LRP and aftermarket additives and handle samples during laboratory analysis. Sampling is conducted manually on a per batch basis from several stopcocks located at various depths on the outside of the LRP finished product tank and also from the additive blending tank. Quality analysis personnel conduct sampling and laboratory analysis once per week for LRP blending and approximately 4 days per year for additive blending.

The main routes of exposure of workers to MMT are dermal and ocular from slops and spills during manipulation of transfer lines and spears and also sampling and laboratory analysis. Despite the possibility of gas leakage if pressurised transfer is used, the low vapour pressure of MMT (0.01 kPa at 20C) renders inhalation exposure of workers unlikely. Once in storage or blending tanks, exposure of refinery or formulation workers during addition to bulk fuel or formulation of aftermarket additives would not be envisaged given the enclosed, automatic nature of the blending/filling processes.

h.4.2Petrol stations and maintenance workshops

Similar exposure, mainly dermal, may be envisaged for petrol station workers during dip measurement of underground tanks. Typically, dipping occurs for up to 10 minutes, once per week. Automechanics at petrol stations and maintenance workshops may be exposed also to diluted MMT in LRP and in aftermarket additives during maintenance of automotive fuel systems. The extent of exposure during these activities is likely to be highly variable.