works and sulphuric acid plant at Merebank, Avonmouth. With the nearby No.23 Filling Factory at Chittening, plus the main plant at Banbury and a third plant at Hereford, construction of the chemical plant began at Avonmouth in 1917, but did not finish until 1923, costing £800,000. The plant came into operation from spring 1918, producing of dichloroethyl sulphide using the Despretz–Niemann–Guthrie process; the chemical agent was then placed into shells on site. Although the first product did not arrive in France until September 1918, two months before the Armistice, it was used that same month during the breaking of the Hindenburg Line within the Hundred Days' Offensive. By November 1918, Chittening had produced 85,424 mustard gas shells. The human cost of producing mustard gas was high. In December 1918 the chemical plant's medical officer reported that in the six months it was operational, there were 1,400 illnesses reported by its 1,100 mostly female workers - all medically attributable to their work. Three people died because of accidents, four died from associated illnesses, and there were 160 accidents resulting in over 1,000 burns. At Chittening there were reported 1,213 cases of associated illness, including two deaths which were later attributed to influenza. Britannia smelting works After World War I, demand for zinc and for sulphuric acid greatly fell, and after running into commercial difficulties it was taken over by a group of British industrialists with interests in metals and chemicals, under whom it was revived. In 1929 the NSC was bought by Australia's Imperial Smelting Corporation, which in 1949 merged with Zinc Corporation to become Consolidated Zinc. After the consolidation, the smaller NSC plants were closed down to concentrate production on Avonmouth - now known as the Britannia smelting works - where the famous Imperial Smelting Process was developed. From 1967, the Avonmouth Works was home to the largest and most efficient zinc blast furnace in the world. Consolidated Zinc, having failed to develop suitable new mining projects, merged from 1962 with the Rio Tinto Company, a mining company. The resulting company, known as the Rio Tinto - Zinc Corporation (RTZ), and its main subsidiary, Conzinc Riotinto of Australia (CRA), would eventually become today's Rio Tinto Group. With smelting cheaper elsewhere in the world, the site ceased production in the 1970s, but remained open as a stock-holding and distribution centre until 2003. In 2012 SITA UK started redevelopment of the site,