During manufacture and use, nicotine formulations used in electronic nicotine delivery systems (ENDS), e.g. e-cigarettes (as e-liquids), and in other (non‑electronic) non-tobacco nicotine delivery systems (NTNDSs), make contact with processing equipment, packaging materials and device components (some examples are given below). Small amounts of chemicals may leach from any or all of these into the nicotine liquids, and subsequently be inhaled by the consumer. This is particularly true of current e-liquid formulations which are primarily a combination of two very good solvents (propylene glycol and glycerin). The Tobacco Products Directive (TPD2) requires that such leachable exposures do not occur in quantities that pose significant health risks to the consumer. Extractables and leachables (E&L) studies play a critical role in ensuring consumer safety, as well as quality control and monitoring.
E&L studies are carried out sequentially by analytical laboratories. First, the contact materials are extracted by various established solvents under exaggerated incubation conditions of time and/or temperature. A range of analytical techniques (e.g. GC-MS, HS-GC-MS, LC-MS, ICP-MS, ICP-OES) are used to identify extractables (sometimes only tentatively or generically); semi-quantification is often possible at this stage. Bibra health risk assessors use the extractables study to identify those extractables that are critical for confirmation and better quantification in a leachables study. Sometimes, a full health risk assessment is carried out by bibra toxicologists on the extractables data.
Leachables studies are then conducted, identifying and quantifying the chemicals that actually migrate into an e-liquid under normal conditions of production, storage for a full shelf-life, and use. Accelerated leaching and/or stability studies using the nicotine formulations can be insightful.
Health risk assessment
Typically, bibra health risk assessments are based on the leachables study results. The consumer exposure is a key element of the assessment, and both the inhaled amount (e.g. µg/day) and the puff concentration (e.g. mg/m3) are relevant parameters. We combine the hazard evaluation of the individual chemicals with exposure information to assess whether any significant local or systemic health risks exist. Worst-case assumptions on exposure and (for unidentified peaks) structure are made to address uncertainties. Where substance-specific hazard data are inadequate, read-across or a conservative Threshold of Toxicological Concern (TTC) approach may be applied. Certain NTNDSs might be classed as medical devices and/or pharmaceutical products. In such cases, the opportunity exists for bibra scientists to take account of guidance from the US Product Quality Research Institute (PQRI) on extractables and leachables in OINDPs.
The end product is an independent, bibra expert risk assessment report explaining transparently whether the consumers are at any significant health risks or not, as a result of leaching substances. This reassures clients or provides the information needed to modify processes, and helps to ensure that consumer health is not compromised by the inevitable low level migration from packaging, processing and device materials.
Examples of sources of leachables
Heating element (vaporiser; metal wire), Canister (tube), Wick, Gasket, Cartridge, Chassis, Funnel, Cage, Valve, Cartomiser (cartridge and atomiser), Cartotank (cartomiser and tank), Plastic end cap, Adhesive, Ink.
Pete and Richard recently gave an interview to Smithers Rapra, about the ongoing safety assessment obligations for e-liquids and e-cigarette hardware…click here to read more!
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