An article published on July 29, 2018, in the peer-reviewed journal Environmental Research, focused on heavy metals found in paints brought on chopsticks. Di Zhao and colleagues from the State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, China, measured total concentrations of lead (Pb), cadmium (Cd), chromium (Cr), cobalt (Co), and nickel (Ni) in paints from “72 wood and 29 stainless steel chopsticks with different colors.” The measured concentrations varied significantly, with ranges being 

0.12-500,000 mg/kg for Pb; 

0.002-120,000 mg/kg for Cd; 

2.2-8400 mg/kg for Cr; 

0.004-2600 mg/kg for Co; 

and 0.10-150,000 mg/kg for Ni. 

The authors summarized that “most samples showed low metal concentrations,” but “high metal concentrations were observed in red and green paints on stainless chopsticks, while paints on wood chopsticks showed lower metal concentrations.” 

For the nine samples that had total Pb > 90 mg/kg, solubilization of all five metals was measured in “simulated saliva, 0.07 M HCL [(simulated gastric fluid)], and 1% citric acid ([acidic food simulant)] solutions.” These experiments represented “exposure scenarios of mouthing, incidental paint ingestion, and metal migration in food,” respectively. Daily metal intakes estimated with incorporation of metal solubilization data showed “negligible” health risk for exposure via mouthing, but “unacceptable” health risk for Pb and Cd via the other two exposure routes. 

The authors conclude that, “to avoid Pb and Cd exposure, use of metal-based paints on chopsticks should be banned, particularly in countries where food is regularly consumed with chopsticks.” 


Zhao, D., et al. (2018). “Metals in paints on chopsticks: Solubilization in simulated saliva, gastric, and food solutions and implication for human health.” Environmental Research 167: 299-30