Leonardo diCaprio as an anti-ager? OK, it's a stretch. But, as an ardent environmentalist, he's fighting to reduce the escalating amounts of pollutants in the air that are harming the planet - and our skin, too. Scientists are just beginning to uncover the full impact on our skin of the daily assault of smoke, smog, fumes and dust. From dullness and greasiness to wrinkles and redness, air pollution isn't just making us cough, it's making us look older too.

According to the World Health Organization (WHO), globally more than 80 per cent of people living in urban areas are exposed to air that exceeds acceptable limits for pollution. But we Brits should be especially concerned. Research has found that dozens of UK cities, including London, Liverpool and Cardiff, will be in breach of EU limits on pollution for at least the next five years; while Oxford Street is the world's most polluted thoroughfare.

"Recent scientific research shows that the skin's greatest enemy is no longer the sun,' says Linda Blahr, national head of training and science at SkinCeuticals. "Ozone pollution surrounds us around the clock. It's proven to cause oxidative stress in the skin by forming free radicals, which in turn leads to visible ageing."

There are five types of pollution particles that affect the skin, each of a different size. But it is PM2.5 - particulate matter under 2.5 micrometres in diameter - that's causing most havoc. Compare it to the average human hair thickness of 70 micrometres, and it's easy to understand how easily these tiny floating aggressors can parachute deep into the pores.

Will an anti-pollution product soon be considered as essential as SPF? Photo / Getty Images
Will an anti-pollution product soon be considered as essential as SPF? Photo / Getty Images

"The skin's natural protection comes from the top 10-12 layers of cells, which act as a barrier," explains Dr Mervyn Patterson, cosmetic dermatologist with Woodford Medical clinics. "As we age, that barrier weakens and pollution particles are able to get through. This causes chronic inflammation as the cells try to protect the skin from these foreign invaders."

The most noticeable effects are pigmentation, redness and uneveness in tone. "The melanocyte cells, which are instrumental in giving skin its colour, become excited, triggering sun spots," says Dr Patterson. "And as inflammation demands more blood supply, the blood vessels become swollen, eventually leading to enlarged red veins and rosacea. Meanwhile, as the cells are being distracted with this, they can also be neglecting to create the collagen needed to keep the skin firm." In other words, over time, you'll start noticing fine lines, wrinkles and crêpey skin.

With pollution levels reaching critical heights, it's no surprise that trend forecasters Canadean predicted pollution protection would be this year's big skincare news. Some cosmetics companies are already ahead of the game, including SkinCeuticals, which has unveiled research that shows a daily sunscreen combined with an antioxidant treatment are the ultimate skin-protecting power couple.

Elsewhere, Lavinia Popescu, senior director for research and development at Elizabeth Arden, has spent five years creating the groundbreaking Prevage City Smart SPF50 Hydrating Shield. The key ingredient is idebenone, a potent antioxidant that is central to neutralising free-radical damage.

"In the lab we've previously used antioxidants for testing the damage done by UV radiation and the specific amounts needed to counteract the free radicals it generates," says Popescu. "Now we're able to demonstrate that we need a different type and amount of antioxidant to protect against and repair the effects of pollution. It's a crucial two-step approach because although we know we can repair some of the damage that pollution is doing to the skin and its DNA, it can only be repaired to a certain point and, as yet, we don't know quite how much."

No particular skin type appears more immune to exposure, either. However: "If you're very fair-skinned or have sensitive skin, you are already more susceptible to UV rays and will also be more vulnerable to pollution," warns Dr Patterson. On the flip side, oiler complexions are also prone. "Big pollution particles will stick to oily skin, while larger pores act like a tunnel for them," says Popescu.

Although many hot new beauty ideas can be relatively flash-in-the-pan, it seems our need for defence against atmospheric enemies goes beyond the buzz. Will an anti-pollution product, then, become as essential a part of our anti-ageing arsenal as SPF?

"It's too early to have any scientific chronological data, but we certainly understand the mechanism of how pollution damages the skin," Popescu says. "In big cities, protection is crucial as damage can be done in as little as a day. And the worrying thing is, we don't know just how much."