Nail technicians are exposed to dangerously high levels of chemicals thought to cause cancer, research suggests.
Scientists studied six salons and found their air contained formaldehyde and other toxic compounds.
Concentrations were beyond what is deemed safe to avoid several forms of cancer, including squamous cell carcinoma, Hodgkin's lymphoma and leukaemia.
And exposure to these chemicals over 20 years could raise a technician's cancer risk by up to 100 times, the researchers claim.
They warn this prolonged exposure may damage a beautician's health as much as working an at oil refinery or garage.
Studies suggest these employees are at risk of asbestos exposure, as well as cancer of the stomach, oesophagus and lungs.
Nail technicians are exposed to dangerously high cancer-causing chemicals (stock)
The study of salons was carried out by the University of Colorado and led by Dr Lupita Montoya.
Dr Montoya has been curious about the effects of airborne chemicals in nail salons ever since a visit to a nail bar a decade ago left her struck by its pungent smell.
She worried the confined space and poor ventilation would expose workers to circulating chemicals, and tried for years to investigate the long-term health consequences nail technicians may face.
However, she soon discovered more than 90 per cent of nail salons are small businesses.
They therefore rarely have the resources to enforce staff health and safety practices, and declined to take part in the experiment.
But in 2017, Ms Montoya and her team convinced six salons in Colorado to participate on the condition of anonymity.
They measured the levels of the chemicals formaldehyde, benzene, toluene, ethylbenzene and xylene in these salons over 18 months.
The nail technicians' cancer risk was then determined according to thresholds set by the US Environmental Protection Agency (EPA) and the Center for Disease Control and Prevention.
Results - published in the journal Environmental Pollution - revealed the salons' formaldehyde concentrations ranged from 5.32 to 20.6micrograms (μg) per cubic metre across the six salons. One microgram is equivalent to 0.001mg.
A cubic metre is commonly used to express the concentration of a chemical in a volume of air. The volume is calculated according to a given metre in height, length and width.
This formaldehyde exposure exceeds the EPA's minimal risk level
