Evaluation of Storage Conditions and Pre‐Treatment Methods to Mitigate Aflatoxin Contamination in Commonly Used Chinese Herbal Medicines

Aflatoxins (AFs) are potent mycotoxins classified by the International Agency for Research on Cancer (IARC) as Group 1 human carcinogens. They posed a major safety concern for Chinese herbal medicines (CHMs), potentially compromising both their efficacy and regulatory compliance. Although imported CHMs in Hong Kong are subject to source‐level quality control, inappropriate local storage under the city's warm humid subtropical conditions may facilitate postharvest aflatoxin production. This study aimed to evaluate the influence of storage temperature and humidity on aflatoxin formation in general CHM storage and to investigate additional measures for the prevention and elimination of aflatoxins. Twenty‐two CHMs susceptible to aflatoxin contamination were selected for analysis. The study was conducted in four phases: (1) a market survey to determine baseline aflatoxin and moisture contents; (2) an experimental assessment of aflatoxin formation under different temperature (4°C, 18°C–22°C, and 35°C) and relative humidity (0%–40%, 40%–70%, 70%–90%, and > 90%) conditions over a 24‐month storage period; (3) evaluation of three pretreatment methods—drying, vacuum packaging, and sulfur fumigation—through both accelerated and long‐term stability tests; and (4) a preliminary investigation of ultraviolet (UV) irradiation as a potential aflatoxin detoxification approach. The market survey detected aflatoxin contamination in specific batches of stirred Hordei Fructus Germinatus (Maiya), Eupolyphaga (Tubiechong), Aspongopus Chinensis (Jiuxiangchong), and Nidus Vespae (Fengfang), with one batch of Aspongopus exhibiting severe contamination. Elevated moisture content was common, particularly among animal‐derived CHMs. Storage experiments demonstrated that high temperature (≥ 35°C) and high relative humidity (> 70%) markedly promoted aflatoxin formation. Optimal storage conditions were identified as cool room temperature (< 22°C) and low humidity (< 70%). All three pretreatment methods effectively delayed aflatoxin production for up to 12 months without compromising the integrity of active components. However, certain CHMs, particularly Corydalis Rhizoma (Yanhusuo), remained susceptible after 24 months. Ultraviolet (UV) irradiation (15 W, 1–4 h) at a vertical distance of 30 cm was ineffective in reducing aflatoxin levels in contaminated samples. In conclusion, strict control of storage temperature and humidity is essential to prevent aflatoxin contamination in Chinese herbal medicines. Pretreatment measures, such as drying, vacuum packaging, and controlled sulfur fumigation, demonstrated effectiveness in delaying aflatoxin formation. Further research is warranted to develop feasible and safe detoxification strategies for materials that have already been contaminated.