Nitrosamines have become one of the most closely scrutinised impurity risks across pharmaceuticals, nicotine and tobacco products, cosmetics, food, drink and other regulated consumer goods. Once viewed largely as a concern in specific food and tobacco contexts, they are now a major focus for regulators and manufacturers because they can form at trace levels under common processing, formulation or storage conditions.
For product developers and marketing authorisation holders, the challenge is no longer simply whether nitrosamines are present, it is whether the potential for formation has been properly understood, assessed, tested and controlled across the full product lifecycle. Here, Dean Hatt, Senior Consultant Toxicology at Broughton, outlines the need-to-knows about nitrosamines, where they are found and how specialist testing can support risk assessment, regulatory confidence and product safety.
Nitrosamines are a class of chemical (N-nitroso) compounds that can form when a nitrosating agent reacts with a secondary or degraded tertiary amine. Nitrosating agents may be present in food preservatives, water, soil, biological systems and some manufacturing inputs, and simply put are any chemical species capable of transferring a nitroso (-NO) group. Amines are organic compounds derived from ammonia, where one or more hydrogen atoms are replaced by carbon-containing groups, and can occur naturally or as part of an active ingredient, excipient, raw material or degradation pathway.
Acidic conditions e.g. the stomach, as well as heat are the catalysts for this reaction, and these are typically provided during processing and storage.
Nitrosamine Risk = Amine Source × Nitrosating Source × Opportunity for Reaction
Although nitrosamines themselves are not always highly reactive, many are considered potent procarcinogens because they can become harmful after metabolic activation, generating reactive intermediates that may damage DNA.
Nitrosamines were first identified as a toxicological concern in the 1950s when researchers found NDMA (N-nitrosodimethylamine) to cause liver tumours in rats. During the next twenty years, scientists identified the potential for nitrosamines to form in foods, and by the 1970s, they were recognised as genotoxic carcinogens capable of damaging DNA and initiating cancer. This led to efforts to reduce nitrite use in food and monitoring was initiated, however, the risk in pharmaceuticals was deemed not to be an issue due to well controlled manufacturing processes.
In 2018, European regulators detected NDMA in Valsartan, a leading anti-hypertensive drug, leading to a global recall and regulatory investigations. Subsequent identification in other sartans, and later Zantac, a leading drug for heartburn and acid reflux, as well as many other medicines confirmed this issue was not isolated to certain manufacturers or products. Here, regulators recognised nitrosamines could arise from the synthesis, reagent impurities, solvent recovery systems, degradation pathways, contamination and even packaging and storage.
Since 2020, Nitrosamine Drug Substance Related Impurities (NDSRIs) were identified, nitrosamines of the drug itself or closely related structures. This expanded the issue widely as almost all medicines containing an amine have the potential to form an NDSRI.
Regulators including the MHRA, EMA and FDA have responded by issuing guidance for risk evaluation, confirmatory testing and lifecycle control. In medicines, marketing authorisation holders are expected to understand possible nitrosamine formation routes, assess risks across active ingredients and finished products, and take corrective or preventive action where needed. Acceptable intake limits are often very low, sometimes in the nanogram-per-day range, reflecting the need to control long-term exposure. A great deal of effort by industry leaders in a collaboration of pharmaceutical companies has enabled a significantly greater understanding of the potency of nitrosamines, the reliability and regulatory acceptability of assays to test their toxicological effects, and this has led to the development of in silico tools to predict them and appropriate analytical methods to detect and measure them at levels that cause concern.
In the tobacco industry, Tobacco Specific Nitrosamines (TSNAs) were identified in tobacco smoke in the 1970s; the most important TSNAs being NNN, NNK, NAT and NAB. By the 1990s, TSNAs were considered among the most-likeliest candidates for causing tobacco-related cancers. Tobacco companies investigated changes to agricultural, curing and processing methods to reduce TSNAs, and as such an important assay for non-combustible nicotine products is to prove the absence of these chemicals.
Effective nitrosamine testing requires more than a single analytical result. Manufacturers need a science-led strategy that starts with product and process understanding, identifies plausible formation pathways, and then applies in silico tools to assess whether the nitrosamine is within a cohort of concern. Finally, appropriate methods capable of detecting compounds at very low levels in complex matrices are developed and applied.
Techniques such as LC-MS, GC-MS and ICP-MS can support the characterisation of nitrosamines and other harmful or potentially harmful constituents, depending on the product type and testing objective. For tobacco and nicotine products, a full HPHC testing programme may include analysis of TSNAs alongside carbonyl compounds, volatile organic compounds and toxic metals. For medicines and healthcare products, since the nitrosamine could be unique to the drug in question, nitrosamine testing tends to be run as a stand-alone event and must be suitably sensitive, specific and validated or qualified at the level deemed necessary for the particular nitrosamine being investigated.
There is no single universal nitrosamine limit that applies across all products. Requirements depend on the product category, intended use, route of exposure, regulatory jurisdiction and toxicological profile of the compound. In the UK and EU, nitrite limits in cured meats are controlled to manage food safety risks, while tobacco-specific nitrosamines are subject to close analytical scrutiny. Cosmetics are controlled under chemical safety legislation, where manufacturers must avoid conditions that promote nitrosamine formation.
In pharmaceuticals, expectations are particularly stringent. The EMA’s nitrosamine framework sets out a three-step approach covering risk evaluation, confirmatory testing and updates to marketing authorisations where required. The MHRA has aligned with this lifecycle approach for products authorised in the UK, reminding marketing authorisation holders that nitrosamine risks must be monitored and mitigated throughout the product lifecycle. The FDA has also issued guidance covering small-molecule nitrosamines and nitrosamine drug substance-related impurities, with recommendations on risk assessment, testing, acceptable intake limits and mitigation strategies.
A robust nitrosamine strategy should bring together toxicology, analytical chemistry, quality, manufacturing and regulatory expertise. The first step is to understand where nitrosation could occur, including the role of raw materials, solvents, reagents, water, excipients, packaging, processing conditions and storage. This enables manufacturers to prioritise the most credible risks and design testing that is proportionate, defensible and aligned with regulatory expectations.
Where risks are identified, appropriate controls may include supplier qualification, specification updates, reformulation, process changes, impurity purge assessments, validated analytical methods, stability studies and ongoing monitoring. For products already on the market, lifecycle management is essential because changes to materials, suppliers, manufacturing sites or storage conditions can alter the risk profile.
Without adequate nitrosamine testing capabilities and processes, manufacturers risk delayed regulatory approval, additional information requests, reformulation costs, product recalls and reputational damage. Working with a specialist testing partner can help organisations detect and quantify nitrosamines and related harmful compounds at trace levels, interpret results in context, and build a risk-based strategy that supports product safety and compliance.
Broughton provides integrated analytical testing, toxicology expertise to predict the potency of nitrosamines, and regulatory consultancy services to help clients manage impurity risks across the product lifecycle. From method development and validation to routine quality control, stability studies, toxicological risk assessment and regulatory support, Broughton works with pharmaceutical, healthcare, consumer and emerging life science companies to develop practical, science-led testing strategies.
Nitrosamine risk is not confined to one industry, one ingredient or one stage of production. It is a lifecycle challenge that requires strong scientific understanding, sensitive analytical methods and proactive regulatory planning. As expectations continue to evolve, manufacturers that invest in robust testing and control strategies will be better placed to protect consumers, maintain compliance and bring safe products to market with confidence.