The extent of UK teenagers' exposure to alcohol and tobacco images and lyrics in YouTube music videos has been revealed in a new study.

An estimated 52.11 alcohol depictions, or impressions, were delivered to each teenager compared with 14.13 to each adult. Individual exposure levels rocketed to 70.68 among 13-15 year old girls.

The pattern of exposure for tobacco was similar to that of alcohol but the overall number of impressions was five times higher.

Researchers found 13 to 15-year-olds saw almost four times as many tobacco images as those aged 25 to 34, research published in the Journal of Epidemiology & Community Health found.

Some music videos contained extensive alcohol and tobacco references, according to the study. These often depicted in a positive light, it was found, and such videos tended to be most popular with younger audiences.

Songs by Beyonce and Pitbull delivered the most alcohol content to teenagers, researchers said.

The study used the results of two online surveys of British adults and teenagers to calculate viewing figures for the 32 most popular music videos of top 40 chart songs in the UK during over 12 weeks.

Researchers analysed the number of 10-second intervals in each of the 32 videos to estimate the total number of  impressions of alcohol and tobacco.

In all, 2,068 people aged between 11 and 18 and 2,232 adults from the age of 19 onwards completed surveys to determine viewing figures for popular videos.

The results suggested the average percentage of viewing across the 32 music videos was 22% for the teenagers and 6% for the adults.

Levels of individual exposure were almost four times higher among teenagers than 25 to 34-year-olds, the figures indicated.

Teenagers aged 13 to 15 received an average of 11.48 tobacco impressions, while those aged 16 to 18 received an average of 10.5. This compares with 2.85 for adults.

Furthermore, exposure was around 65% higher among girls, with the highest numbers of tobacco impressions delivered to 13-15 year olds.

Trumpets by Jason Derulo and Blurred Lines by Robin Thicke delivered some of the highest number of tobacco impressions, while Timber by Pitbull and Drunk in Love by Beyonce delivered the most alcohol content.

The researchers wrote: "If these levels of exposure were typical then in one year music videos would be expected to deliver over 4bn impressions of alcohol and nearly 1bn of tobacco in Britain alone.

"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."

A ban on paid-for placement of branded tobacco products has been in force since 2002 in the UK, while alcohol promotion is regulated by the Advertising Standards Authority.

While films are classified and TV content is subject to controls during periods when children are likely to be watching, no such regulations apply to digital music videos.

The evidence suggests teenagers exposed to depictions of alcohol and tobacco content in films are more likely to start smoking or drinking.

The researchers concluded: "Owing to the obvious health implications for adolescents, we suggest that overly positive portrayals of both alcohol and tobacco in music videos should be included in both the drug misuse and dangerous behaviour presented as safe rating categories."