If you have product that isn't coming with lab testing there really isn't much way to know for sure without lab results. one trick you may be able to use is to ask for samples and send the samples off to a lab yourself. It may be a bit pricey up front but your health is worth the added cost if you're going to be using it long term or "seriously". many people think of heavy metal poisoning being a sudden event but not everyone considers that these toxins can build up slowly over time and the harm that they can do . once you know for sure that your vendor has "clean" product you might be better off to buy in bulk and do a final lab on the bulk shipment. the first test or so should really only be used as a test of faith.

best of luck, feel free to message me if you need anything.