Health authorities yesterday recalled a botched Chinese herbal concoction after a woman received hospital treatment for chemical poisoning. The 42-year-old sought treatment at Princess Margaret Hospital on April 28 after drinking herbal medicine. She was discharged on Sunday. A Department of Health investigation traced the poisoning case to sodium nitrite, which was confused for the traditional Chinese herb natrii sulfas. A wholesaler and 20 retailers were ordered to recall the batch. Chinese herbalists and traders were also put on alert about the possible mislabelling. 'Upon tracing of the source, the erroneous substitution was at the wholesale level,' a department spokesman said. The main chemical component of natrii sulfas is sodium sulfate. It was used as a laxative, for cooling the body and decreasing oedemas, the Department of Health said. But sodium nitrite is a chemical that is not used as a Chinese medicine. It is commonly used, however, as a colour fixative and preservative in meats and fish. It is also used in western medicine as a bronchial dilator and an intestinal relaxant. According to the department, ingesting highly purified sodium nitrite will result in a lack of oxygen in body tissue. The department is investigating if any laws were violated. Meanwhile, the Food and Environmental Hygiene Department was seeking information from its mainland counterparts after some brands of the popular Longkou green bean vermicelli were reportedly found with chemicals that could pose a serious health threat.