Online music videos 'expose teens to smoking and drinking'
Online music videos are heavily exposing teenagers to positive depictions of smoking and drinking alcohol, research suggests.
Such portrayals posed a "significant health hazard that requires appropriate regulatory control", researchers said.
YouTube videos of songs in the top 40 singles chart were examined by the University of Nottingham study.
The British Board of Film Classification started putting age ratings on online pop videos last year.
The research, in the Journal of Epidemiology and Community Health, said girls between the ages of 13 and 15 were the most exposed to cigarettes and alcohol in videos.
Using pollsters YouGov, researchers asked 2,068 11- to 18-year-olds and 2,232 over-19s whether they had seen the videos, taken from the chart between 3 November 2013 to 19 January 2014.
The average viewing percentage across the 32 music videos was 22% for the younger group and 6% for the elder.
Trumpets, by Jason Derulo, and Blurred Lines", by Robin Thicke, had some of the highest number of tobacco references, while Timber, by Pitbull, and Drunk in Love, by Beyonce, contained the most alcohol-related content, according to the study.
"It is well established that young people exposed to depictions of tobacco and alcohol content in films are more likely to start smoking or to consume alcohol, but the effect of imagery in other media, including new online media such as YouTube music videos, has received relatively little attention," research author Dr Jo Cranwell said.
Her research calculated the number of "impressions" - any verbal or visual reference - of alcohol or tobacco imagery in the videos.
When Dr Cranwell extrapolated the data to estimate the overall affect on the British population, she concluded the 32 videos were responsible for 1,006 million impressions of alcohol and a further 203 million of tobacco.
"If these levels of exposure were typical, then in one year, music videos would be expected to deliver over four billion impressions of alcohol, and nearly one billion of tobacco, in Britain alone," she said.
"Further, the number of impressions has been calculated on the basis of one viewing only, however, many of the videos had been watched multiple times, so this number is likely to be much bigger."
Here are a selection of lyrics from Beyonce's Drunk in Love that reference drinking and smoking:
I've been drinking, I've been drinking. I get filthy when that liquor get into me
Boy, I'm drinking, get my brain right, Armand de Brignac, gangster wife
Cigars on ice, cigars on ice
Paid-for placement of tobacco products in music videos is prohibited by the Advertising and Promotion Act 2002, but this law does not apply to videos produced outside the UK.
Last year, it was announced that online music videos would now get age ratings in the same way films do, following a government pilot.
Sony Music, Universal Music and Warner Music will send videos to the British Board of Film Classification before putting them on YouTube and Vevo.