NDMA is not a known carcinogin, like methylene chloride. It's a suspect carcinogin, which means it hasn't been proven to cause cancer in anything but lab animals, usually in ultra lage doses. Here's the to see for yourself. The FDA may have a hidden agenda here.

While NDMA could cause harm in high amounts, the levels found in some medications are not much more than what’s commonly found in foods and dairy, according to the FDA.

I know the above doesn't mean there's no cause for concern, but figure it's important to understand the level of risk/seriousness this presents.

High amounts are harmful. I have been taking this occasionally for years. Every time l buy it, l notice the strength is doubled. I spend time looking for the original dose. I am sure there is no connection.