From www.consumerlab.com :

Magnesium:
17 of 19 products pass testing. Failures on dose and lead contamination.

Weight Loss, Slimming, and Diabetes-Management Supplements (Chromium, CLA,
and Pyruvate):
More than one in five supplements fail ConsumerLab.com evaluation.

ConsumerLab.com is currently testing...
Omega-3 and 6 Fatty Acids (from Evening Primrose, Flaxseed, and Borage
Oils), Potassium Supplements, Iodine Prophylaxis Supplements for Nuclear
Accidents (Potassium Iodide), Garlic, and Sexual Enhancement Supplements

Theola