He said second-hand smoke contained more than 4, 000 chemicals, including benzene, formaldehyde, arsenic, ammonia and hydrogen cyanide.

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For example, two chemicals -- chlorine and hydrogen cyanide -- that were used with devastating effect as weapons in World War I are explicitly exempted from the CWC's prohibitions.

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For her experiment she studied the inheritance of three traits: a maroon coloured leaf marking, a white V-shaped leaf mark pattern, and the production of hydrogen cyanide in damaged leaves, which is thought to be a defence against predators.

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Having harvested and germinated seeds from her hand pollinated plants, Minushika scored those seedlings for presence or absence of the red fleck and white V leaf marks and assayed for a specific genetic precursor and enzyme need for the production of hydrogen cyanide.

UNESCO: Outstanding Student Award - Realise the Dream