Levels of Cu, Zn, Pb, and Cd in the leaves of the tea plant (Camellia sinensis) and in the soil of Gilan and Mazandaran farms of Iran

Tea is known as an inevitable and important part of a healthy and balanced diet. However, it might be contaminated by heavy metals via many ways, including irrigation by sewage water, industrial effluents, sewage sludge, vehicular emissions, industrial wastes, and atmospheric deposition. The concentrations of Cu, Zn, Cd, and Pb elements in the leaves and soil samples of the tea farms in North Iran were determined by using flame and graphite furnace atomic absorption spectrometry. The samples were digested with the concentrated nitric acid and perchloric acid. The descending sequence of the mean metal levels in the tea leaves is as follows: Zn > Cu > Pb > Cd. The content of heavy metals in the tea samples were found and are provided in the following ranges: 6.07–15.24, 55.35–127.22, 0.03–0.64, and 0.06–0.38 µg/g for Cu, Zn, Pb, and Cd, respectively. According to the Institute of Standards and Industrial Research of Iran (ISIRI), the tolerance limits have been adjusted only for copper, cadmium, and lead. However, the present database can be employed for fixing the tolerance limit of zinc in tea. The contents of copper and lead in tea were significantly lower than the permissible limit under the ISIRI act. In contrast, the cadmium concentration was significantly above the permissible limit ( P