A New Look at Carbon Disulphide as a Grain Fumigant

Abstract

Although carbon disulphide (CS2) is an old fumigant, the possibility of reintroducing it is supported by new data from Australia, and by published Egyptian and Chinese data which is not widely known. The data covers grain quality, natural emissions and residues in processed food. Egyptian data shown that CS2 has no effect on the germination and plumule length of rice even at high doses (400 mg/m3). Chinese data has shown that CS2, at high doses (200 mg/m3), has no effect on the germination of a large number of seeds, including malting barley, wheat and maize, sorghum, cotton, carrot etc. This is supported by current Australian data (150 mg/m3) on germination and plumule length of wheat, barley and chickpeas. Australian data from the Stored Grain Research Laboratory (SGRL) commercial scale trial showed that all tested insects are killed by CS2 at a range of C´T (concentration´time) values of 1 000~1 500 mg·h·L–1 and has no effect on the quality of end products of wheat. The sorption of carbon disulphide on grain is lower than that for methyl bromide, and is mainly physical in origin. It leaves residues on grain, but these are extensively degraded during storage and processing. Remaining residues of CS2 are reduced during cleaning and conditioning of wheat before milling. Residues of CS2 are progressively reduced during the milling and baking processes. For example, wheat was treated at 27 g/m3 of CS2 for 6 days in sealed farm bin and then aired for 24 hours. Cleaning reduced residues from 6.7 to 4.6 mg/kg, and conditioning reduced residues from 4.6 to 2.2 mg/kg before milling. They are further reduced during milling, and further still during formation of noodles (even before cooking), pasta and bread. Residues in processed products were indistinguishable by current methods of analysis (limits of quantification were <0.005 mg/kg) and the same as levels present in products made from unfumigated wheat from the same source.

Keywords

• fumigant
• carbon disulphide
• sorption
• germination
• residues