The definite article and zero article

The replacements which the chemical industry is developing for CFCs are also potent greenhouse gases.

In the early 1980s, at a time when manufacturing industry was collapsing and the outlook for the unskilled looked particularly bleak, frustration boiled over in a series of riots in London, Bristol, Birmingham, Liverpool, and elsewhere.

In the above sentences, I would like to aske why one industry is preceded with the definite article while the other is not(zero article).

Thank you.

The chemical industry is a single industry, but there are many different industries that manufacture- cars, shipbuilding, etc.

:up: