By 
The last hundred years have seen an explosion of man made products that we use or consume almost every day. These did not exist in nature and even if they did, not in items of everyday human use.
We use new materials to prepare or package food. We use plastic containers, teflon coated cooking utensils, and more.
We use a whole lot of chemicals in our cosmetics. Hair cream, skin cream, perfume, deodorants, toothpaste, hair colors, and more.
There are a large number of synthetic flavours, colors, preservatives, additives that are added to our food.
We have pesticides, herbicides, fungicides used to grow our food and to store and transport it.
There are a lot of new man made medicines and drugs, as well as implants made of new materials.
Some of these new things get disallowed and do not enter widespread use because they cause rapid toxicity. It becomes apparent within a few months or years that they are causing disease or cancer.
However, some of them don’t get linked to disease or cancer for many decades and, in those things, especially when entire industries are dependent on them, mere suspicion or some correlation does not suffice to take them out of circulation.
With the passage of time, the burden of proof shifts to the consumer.
I will argue that many of the things we use everyday are possibly unsafe for long term sustained use. But we may not know which ones. Not in our lifetimes.