Improved refining technology and the use of more low-sulphur oil have helped cut emissions.

However, domestic supplies of low-sulphur oil were inadequate to meet the potential demand and the oil embargo of 1973 dramatically highlighted this problem.

In the early 1980s, light-grade, low-sulphur oil was discovered near Deir ez-Zor in eastern Syria.

Test drilling began in 1966 and then, in 1969, Phillips Petroleum Company discovered the Ekofisk oil field distinguished by valuable, low-sulphur oil.

Complicating factors have included questions on when Iraqi oil would come back on the market, increasing demand for diesel fuel for trucks and trains and jet fuel for commercial airliners and the willingness of European customers to pay high prices, especially for clean, low-sulphur oil.

The increasing price of low-sulphur oil and the reluctance to rely upon imported oil in the future brought a growing demand by industry and by some politicians for the adjustment of the 1970 Act requirements in the light of economic and energy realities as well as technological practicability (Lundqvist, 1980).

One of the successes of the bubble policy to date includes a plant in Providence, Rhode Island, where $2.7 million was saved by replacing expensive low-sulphur oil at its two plants, one with high-sulphur oil and one with natural gas, which also resulted in a net reduction of the sulphur dioxide emission (Smith, 1981).