Lead? Great material, tastes good in wine! Stops knocks in gasoline! Kills our children.
Asbestos? Wonderful insulator! Great cheap material for keeping buildings warm during the winter. Causes cancer.
Margarine? Lower calories than butter, almost tastes just like it! Causes heart disease.
Teflon? Awesome for non-stick pans! Non-stick all the things! Causes cancer.
Benadryl? Great anti-allergy med, dries you up and helps you sleep during hay-fever season! Causes dementia with extended use.
BPA? Great cheap material for making water bottles and food containers... Causes cancer.
Peppermint flavored Tums... The binding agent for the peppermint was a possible carcinogen. They pulled mint-flavored Tums off the market for a while until they could figure out a new way to make it.
We already see microplastics causing mutation and other issues in sea life. Why would we expect this to go any differently than what we've been learning about all these other modern conveniences?
But there are errors in the other direction too. How many deleterious effects will never be proven scientifically because it's incredibly exhausting to get thousands of participants and quantify their subjective wellbeing in a controlled way?