A study in the late 1980s showed 37 out of 67 samples of potatoes contained tecnazene (a chemical used to stop sprouting) above the maximum residue level in the UK. By 1990 this had decreased dramatically because the maximum residue level had been raised from one to five milligrams per kg. Similarly with carrots: after finding residues of triazophos (an insecticide which is a chemical descendant of nerve gas) at ten times the maximum residue level, the Ministry raised the acceptable level by a factor of 20.