In 2018, a research team centered around Hokkaido University has published a study revealing that neonicotinoid pesticides were detected in all samples of commercially available Japanese green tea leaves and bottled tea beverages. In contrast, no pesticides were detected in tea leaves from Sri Lanka, highlighting the impact of pesticide use in domestic tea leaf production in Japan.
In the study, the team investigated the residues of neonicotinoid pesticides and their metabolites in 39 samples of Japanese tea leaves, 30 samples of Sri Lankan tea leaves, and 9 samples of bottled tea beverages purchased from domestic convenience stores. As a result, no pesticides were detected in the Sri Lankan tea leaves, but seven types of neonicotinoid pesticides, including dinotefuran, were detected in the Japanese tea leaves, and six types (excluding nitenpyram) were detected in the bottled tea beverages. Although the estimated intake was lower than the acceptable daily intake (ADI), the study suggests that long-term or excessive consumption may pose health risks.
The detection frequency and maximum concentration of pesticides were highest for dinotefuran (100%, 3004 ng/g), followed by imidacloprid (92%, 139 ng/g), thiacloprid (79%, 910 ng/g), thiamethoxam (79%, 650 ng/g), clothianidin (74%, 233 ng/g), acetamiprid (67%, 472 ng/g), and nitenpyram (3%, 54 ng/g). Dinotefuran was also the most frequently detected pesticide in the tea beverages. Although all detected values are below Japan's maximum residue limits for tea leaves, the study points out that Japan's limits are higher compared to those in the EU and other regions. For acetamiprid and clothianidin in bottled tea, the United States has higher limits than Japan, but for other pesticides, Japan's limits are set higher.
The paper also highlights that, compared to adults, children are more vulnerable to the effects of these pesticides. Additionally, there are gaps in understanding the toxicity of neonicotinoid pesticide metabolites. Therefore, the study emphasizes the need for further research on the toxicity of these metabolites and large-scale epidemiological studies on environmental exposure to clarify the risks and safety of these pesticides.
((Reference))
Yoshinori Ikenaka, et al. “Contamination by neonicotinoid insecticides and their metabolites in Sri Lankan black tea leaves and Japanese green tea leaves” . 「Toxicology Reports」 Vol. 5, 2018, pp. 744-749.
