The safest I know of are infrared saunas (red bulb/near infrared is best), and breathing exercises, as well as overall good nutrition and emotional healing to support the body's natural detox pathways.
Clinical practices like intravenous chelation (ETDA etc) or supplements like spirulina, ALA, NAC, vitamin C, cilantro etc are popular and seem appealing from the promises made in their marketing, but they are often ineffective at removing the most deeply-stored toxins, and can do more harm than good by moving some toxins around the body to places where they can do more damage.
Clinical practices like intravenous chelation (ETDA etc) or supplements like spirulina, ALA, NAC, vitamin C, cilantro etc are popular and seem appealing from the promises made in their marketing, but they are often ineffective at removing the most deeply-stored toxins, and can do more harm than good by moving some toxins around the body to places where they can do more damage.