GMB mid-Cheshire branch secretary Jim Cairns is worried that bin men will be harmed by fumes from rubbish left to rot for a fortnight at a time.
SITA started collecting recyclables one week and non-recyclables the next in Vale Royal, Cheshire, this week.
And following a campaign headed by opposition Labour councillor Brian Lloyd, Cairns is monitoring the scheme closely.
If there is a build up of gasses in the refuse bags, then its our members in the firing line, said Cairns.
The council issued a page advert telling people to wrap their rubbish up properly why are they doing this if there is no danger?
If our members run into problems then we will see what they want to do about it. It is a bit concerning.
Lloyd has fronted a campaign against alternate-week collections after concerns from residents.
Research from Scandinavia has shown that waste left in bins for a fortnight will start to putrefy and give off gases that inflame the lung tracts of those working with them, he said.