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Some restaurants celebrate customers’ special occasions by planting burning sparklers onto food, showering it with sparks. Sparklers typically contain an oxidising agent such as potassium nitrate, which yields nitrite as a combustion product. The European Food Safety Authority specifies a safety limit for nitrite ingestion of 3.7 milligrams per day per kilogram of body weight. How much nitrite would someone ingest by eating a slice of sparkler-enhanced birthday cake?

John Gordon, Datchworth, Hertfordshire, UK

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