Comparison of Regulations for Arsenic and Heavy Metals in Herbal Medicines Using Pharmacopoeias of Nine Counties/Regions

Introduction Standardization is an import factor in ensuring the safety, efficacy, and quality of herbal medicines, and facilitates their international commerce. Heavy metal poisoning due to herbal medicines has been reported in many countries. Here, to better understand the current state of harmonization, we compared regulations for arsenic and heavy metals in herbal medicines across seven countries and two regions with two international standards. Methods We studied the monographs of herbal medicines of seven countries and two regions, as well as the WHO guidelines and ISO standards. We then compared the limits and test methods adopted for elemental impurities in herbal medicines listed in the monographs and standards among countries. Results The number of herbal medicines assessed amounted to over 2000. Limits and test methods adopted for elemental impurities in herbal medicines varied by country/region and organization. Although WHO recommends a uniform upper limit for lead and cadmium for all herbal medicines, some countries set unique upper limits for individual herbal medicines. ISO 18664:2015 lists only instrumental analysis methods, whereas Japan and India list only chemical methods. Conclusions Many countries do not adhere to the WHO or ISO recommendations on elemental impurities in herbal medicines. These findings suggest the presence of differences in regulations for herbal medicines among countries/regions, likely rooted in cultural differences and policies aimed at maintaining the diversity of herbal medicines. Regulatory convergence by “loose harmonization” to internationally agreed standards appears a feasible option to maintain diversity and safety, and promote international trade in herbal medicines.