500 cigarettes beat 500 Cigarettes Meme: 'The Orville'

At weeks 0, 4, 12 and 24, the researchers sampled participants urine, testing for the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, also known as NNAL

Contributor to The Irish Times, writing about health, science and innovation

Dimensions: Approximately 8 x 10.75 inches

If someone smokes one cigarette instead of 20 per day, intuitively wed think that the risk drops to one in 20, or five per cent, says lead author Allan Hackshaw, a professor at University College London, whose paper analysed 141 previous studies

It can also make asthma worse

Tip: If the interior of the filter becomes visibly saturated with dark brown or black tar, it's time to switch to a new one