The disea — se provisions of the 1971 Act are the least stringent of the three Acts. Section 29(1) of that Act requires only that '...any employment of the employee by the Commonwealth was a contributing factor to he contraction of the disease...'. As no minimum degree of contribution by employment is specified by that Act, this appears to be a very broad criterion.
Under the 1971 Act, the medical issue 'would the employee have contracted/ aggravated the disease had it not been for the influence of employment?' may very well be answered 'Yes!', without that answer necessarily extinguishing liability. The 1971 Act requires that employment contribute to the disease, but does not require it be a critical or principle cause.
Nevertheless it is an accepted principle that the degree of contribution must be more than trivial, and must be capable of influencing the advent and/or course of the disease.