To further investigate the prevalence of tea-drinking-borne endemic fluorosis in Tianzhu Tibetan Autonomous County (referred to as Tianzhu) Gansu Province, to accurately master the information of patients with tea-drinking-borne endemic fluorosis, and to provide scientific basis for popularizing low fluoride brick tea and carrying out patient rescue and treatment.

From 2019 to 2020, according to the "Investigation Plan of Tea-drinking-borne Endemic Fluorosis in Gansu Province in 2019", in the administrative villages with the habit of drinking and selling tea, drinking water samples of local residents were collected to detect the fluorine content of water in Tianzhu, 10 families were randomly selected in each village, basic situation of each family member and the drinking situation of tea were investigated, and tea samples were collected to determine the fluorine content. At the same time, all children aged 8 - 12 in the investigation village were examined for dental fluorosis; clinical examination of bone and joint symptoms and signs was conducted for permanent residents over the age of 25 in the investigation village (excluding 25 years old), X-ray examination of bone and joint was conducted for patients with clear clinical symptoms or signs of skeletal fluorosis, and urine samples were collected to detect urinary fluorine. Ion selective electrode method was used to detect fluorine in water, tea and urine, and dental fluorosis was diagnosed by "Diagnosis of Dental Fluorosis" (WS/T 208-2011), and the "Diagnostic criteria for Endemic Skeletal Fluorosis" (WS 192-2008) was used for the diagnosis of skeletal fluorosis.

A total of 161 water samples were collected, and the fluorine content in water was from 0.07 to 0.68 mg/L, which met the domestic drinking water standard ( < 1.0 mg/L). A total of 1 644 side-tea samples were collected, and the annual per capita consumption of side-tea of permanent residents over 16 years old was 1.05 kg. The average fluoride content of tea was 601.99 - 991.38 mg/kg. According to the detection results of tea fluorine, 16 administrative villages with an average daily intake of tea fluorine more than 3.5 mg/d were screened, the lowest intake was 4.91 mg/d in Tuta Village Danma Township, and the highest intake was 18.98 mg/d in Huashan Village Maozang Township. A total of 253 children aged 8 - 12 years old in 14 administrative villages were investigated. There were 3 cases of very mild dental fluorosis, 2 cases of mild dental fluorosis, and 1 case of moderate dental fluorosis. The overall prevalence of dental fluorosis was 4.74% (12/253). The clinical examination of bone and joint symptoms and signs was carried out for 3 100 permanent adults over the age of 25 (excluding the age of 25) in 15 administrative villages. The X-ray examination of bone and joint was carried out for 104 patients with definite clinical symptoms and/or signs of skeletal fluorosis. Six patients with skeletal fluorosis were diagnosed, including 3 mild and 3 severe, aged 56 - 76 years. The average urinary fluorine in the investigated villages was 0.73 - 4.74 mg/L (the number of investigated was 3 100). According to the determination and classification standards of tea-drinking-borne fluorosis area, Tuta Village Danma Township, Xiding Village Dahonggou Township and Daiqian Village Zhuaxixiulong Township were determined to be in the mild area of tea-drinking-borne endemic fluorosis, while Nannigou Village Zhuaxixiulong Township was in the moderate area of tea-drinking-borne endemic fluorosis.

Tea-drinking-borne endemic fluorosis is prevalent in Tianzhu, Gansu Province, and targeted prevention methods and control measures need to be taken.

Tea; Fluoride; Content; Fluorosis