Is there still a need to be supervigilant about exposure to toxins at 65?

Toxins. Toxins do not discriminate based on age. They cause harm at any age. So "yes" if you have been super vigilant no need to change now that you are 65yrs.
Complicated. There are many toxic heavy metals, plastics etc that can accumulate in your body but it is unclear if they affect you. Most are in insanely small amounts and cannot be shown to cause problems. Other chemicals such as mercury and lead have known toxicity and can cause harm. These are best treated by avoiding them in the first place. Do not buy the worthless detox products you see.