HPMC capsules have been widely studied and are the most common form of capsule used in the nutrition supplement and pharmaceutical industries.
Their made from a plant based cellulose, extracted from plant fiber & are easily broken down in the digestive tract.
Regulatory bodies like Australia's TGA & others across the world have approved its use & require extensive, ongoing testing for contaminants.
So we don’t have any issues with using HPMC capsules.