Some over-the-counter toothpastes have been found to contain arsenic levels above 200 parts per million—far exceeding international safety limits.
In a systematic review, researchers investigated the presence and concentration of heavy metals in over-the-counter toothpastes by synthesizing findings from in vitro studies across multiple regions. They aimed to assess the extent of heavy metal contamination and its potential implications for human and environmental health.
"Although some heavy metals such as cadmium, lead, mercury, arsenic and silver are toxic and must not be present in toothpastes, there are other heavy metals that are essential in small quantities but could result in adverse effects if present in excess," noted the researchers.
They conducted a comprehensive literature search across 6 databases—Google Scholar, PubMed, Scopus, Springer Link, Embase, and Web of Science—yielding 9,409 articles. After removing duplicates and applying predefined inclusion criteria based on the PICOS framework, 11 studies were included. Data extraction was performed using Covidence software, and study quality was assessed using the Quality Assessment Tool for in vitro Studies.
Among the 11 studies, 7 demonstrated a high risk of bias and 4 showed a medium risk, primarily because of insufficient reporting of sampling methods and sample size calculations, according to Kavery Chengappa, of the Manipal College of Dental Sciences Mangalore at the Manipal Academy of Higher Education in Karnataka, India, and colleagues.
All of the included studies reported the presence of both essential and toxic heavy metals in toothpaste samples. Detection methods varied, with eight studies using atomic absorption spectrophotometry, two using inductively coupled plasma–mass spectrometry, and one employing microwave plasma–atomic emission spectrometry. Toxic heavy metals identified included cadmium, lead, arsenic, mercury, and silver. Essential metals such as zinc, iron, copper, cobalt, chromium, and nickel were also found in varying concentrations.
One of the studies reported cadmium levels ranging from 2.008 to 55.28 ppb, lead from 1,856 to 6,313 ppb, and arsenic from 0.6 to 26.94 ppb in toothpaste samples marketed in Saudi Arabia.
In a study of Maltese toothpastes, researchers observed lead concentrations between 2.37 and 12.04 ppm and silver levels from 2 to 5.12 ppm.
In Nigeria, researchers identified lead in all 35 toothpaste samples studied, with cadmium present in 26. In another study, researchers found arsenic levels of 209.33 to 221.96 ppm, lead at 75.86 to 78.31 ppm, and cadmium between 8.8 and 9.19 ppm, all exceeding the maximum permissible limits set by regulatory agencies including the U.S. Food and Drug Administration and the World Health Organization.
The findings support the need for regulatory oversight of heavy metal content in personal care products to mitigate potential risks of bioaccumulation and environmental toxicity.
The researchers reported no conflicts of interest.
Source: Frontiers of Dental Medicine