'anti-environmental' is formed by the prefix 'anti-' (from Greek 'anti-' meaning 'against') combined with 'environmental' (from 'environment' + the adjective suffix '-al').

'Environment' comes from Old French 'environ' / 'environer' (to surround) and entered Middle English as 'environ' and later 'environment'; the adjective 'environmental' was formed by adding '-al'; the compound 'anti-environmental' is a modern formation combining 'anti-' with 'environmental' to describe opposition to environmentalism or environmental protection.

Originally 'environment' simply meant the surroundings or what surrounds something; over time 'environmental' took on senses related to conservation and ecological concern, and 'anti-environmental' came to mean actively opposed to those conservation or pro-environment policies.