29 March, 2021—RLX Technology(RELX)’s latest peer-reviewed study published in Journal of Applied Toxicology showed the cooling agent WS-23 widely used in e-cigarette has limited impact on the experiment animals at the tested dose.
The study showed that there were no deaths in any of WS-23 treated groups in the acute and subacute inhalation studies, with no remarkable changes occurred in body weight, organ weight, hematology, and serum biochemistry, and no toxic effects in the histopathologic analysis.
It was the first study published on the Science Citation Index (SCI) indexed journal conducted by Chinese e-cigarette industry.
WS-23 is a well-known artificial synthesis cooling agent widely used in foods, medicines and tobaccos. As a commonly cooling agent in e-cigarette liquids, WS-23 has led to concerns about the inhalation toxicity with the prosperous of e-cigarettes in recent years. The study shows that at the tested dose level, inhalation of WS-23 will not bring toxic side effect to test animals.
“Product safety has always been RLX’s top concern, and it is also the direction and commitment in our research and development,” Xingtao Jiang, head of RELX Lab. Before the study was published, RELX Lab has conducted vitro tests to prove the aerosol containing WS-23 is safe to use in the products. The latest assessment has further discovered the inhalation toxicity of WS-23 used in the product. Jiang said RLX will continue to conduct more studies to improve RELX products’ quality.
The study was led by RLX science team and part of the experiment were conducted in its physiochemical lab.
In the experiment, Specific-pathogen-free (SPF) SD rats were used to inhale the diluted aerosols of WS-23 with different concentrations and blank solvent by a nose-only exposure system, taking clean air as the control group. After the administration period and the recovery period, the researchers evaluated the acute and subacute inhalation toxicity of the cooling agent WS-23 by comparing key indicators with control groups.
In the acute inhalation study, the appearance, behavioral activities, feed intaking and excreta of all rats seemed to be no obvious abnormalities in the recovery period. In the subacute inhalation toxicity study, there was no significant difference observed in the body weights, feed consumption and relative organ weights. Hematological, serum biochemical, urine and bronchoalveolar lavage fluid analysis also revealed the non-adverse effects after 28-day repeated WS-23 inhalation.
In conclusion, the maximum tolerated dose for WS-23 acute inhalation is not less than 340 mg/m3 , and the No Observed Adverse Effect Level (NOAEL) of WS-23 subacute inhalation was determined to be over 342.85 mg/m3 .
In September 2020, RLX has announced its plan to conduct strict product quality study, physiochemical study, pathological, clinical study and the evaluation of long-term use of e-cigarette. The WS-23 study was the first publicly published scientific achievement.