Cool. Don't use them.
>> often they leave their diesel motor running
Seems a genuine concern. I suggest you voice your concerns to the operator whenever it happens. Escalate to authorities if it becomes a serious problem.
>> ice cream vans (and hand car washes) carry modern slavery risks in the UK
Not cool. Please don't denigrate an entire class of something you dislike using FUD. Even if it's true occasionally, it's certainly not true in general.
I said that they carry modern slavery risks in our country at the moment. There is plenty of data to support the claim that hand car wash businesses carry this risk; there was recently an initiative to help identify known problem businesses with an app: https://www.bbc.co.uk/news/uk-england-47829016
I recently found out that the ice cream van near us that I have used before is part of a network of vans all around my city that has been linked to modern slavery. It’s not an isolated incident in my part of the country.
I don’t think my statement in regard to the modern slavery risks denigrated the ice cream van industry. If I said ‘don’t use ice cream vans because they are all run by slave masters’ then I would have been tarring the whole industry with the same brush. But I didn’t say that.
Human trafficking is a real thing. Coffeedoughnuts provided a link with a news story about an app that has been used to report businesses suspected of engaging in that industry.
My proximity to your smoke machine does not prove that I am on fire.
I would add that the linked article, which is about car washes not ice-cream vans is equally FUD-driven. Weasel words like "linked to", "concerns", "thought to be" are used frequently, but no hard evidence of slavery is presented.
Slavery is a crime in UK. If there have been successful prosecutions and those demonstrate prevalence, rather than sporadic occurrence in an industry, then your blanket aspersions might be justified.
Otherwise, please refrain. Such FUD is likely to needlessly harm the business of law-abiding traders.