1. Work involving exposure to any of the following substances:
(a)beta-naphthylamine or methylene-bis- orthochloroaniline;
(b)diphenyl substituted by at least one nitro or primary amino group or by at least one nitro and primary amino group (including benzidine);
(c)any of the substances mentioned in head (b) if further ring substituted by halogeno, methyl or methoxy groups, but not by other groups; or
(d)the salts of any of the substances mentioned in heads (a) to (c).