Working near busy roads triggers breast cancer, scientists warn after they found at least six women at the same bridge got it within three years of one another.
The group of women all developed a cancer believed to have been caused by exhaust fumes in what researchers have branded a ‘new occupational disease’.
There is a one in 10,000 chance the cases were a coincidence, the study said, because the cancers were all so similar and close together.
And another group of seven women developed the disease after working at a tunnel just four miles away at the border between the US and Canada.
Despite scientists going as far as to label a new disease after one woman’s ordeal, she was denied any compensation by the Canadian government.
Women working at the Ambassador Bridge (pictured), which connects Detroit and Ontario in North America, were found to have a 16 times higher risk of getting breast cancer than the average population, because around 27,000 vehicles use the road every day
Research focused on the case of one unnamed woman who worked for 20 years at the Ambassador Bridge between Detroit, Michigan and Windsor, Ontario.
The bridge connects the US with Canada and is the busiest commercial border crossing in North America, seeing 12,000 trucks and 15,000 cars every day.
Assuming the volume of traffic was the same over the woman’s 20-year employment and she worked 40 hour weeks, she could have been exposed to the fumes of up to 46.8million vehicles.
Doctors Michael Gilbertson and Jim Brophy, from the University of Stirling in Scotland, believe chemicals in the traffic fumes caused the cancer.
They say the BRCA1 and BRCA2 genes, which try to stop tumours growing, can be shut down by vehicle exhaust fumes.
‘These outbreaks of breast cancer represent a new occupational disease,’ said Dr Gilbertson.
These women’s cases revealed working in the toll booths gave them a 16 times higher chance of breast cancer than the average woman.
The woman in the case study developed breast cancer when she was 44, and then again at the age of 51.
Her diagnosis came within 30 months of five other women working at the same border crossing.
And at the Detroit-Windsor tunnel, four miles away, another seven women were developing the same disease alongside them.
What is the BRCA gene and how does it affect people’s risk of cancer?
Having a mutated BRCA gene – as famously carried by Angelina Jolie – dramatically increases the chance a woman will develop breast cancer in her lifetime, from 12 per cent to 90 per cent.
Between one in 800 and one in 1,000 women carry a BRCA gene mutation, which increases the chances of breast and ovarian cancer.
Both BRCA1 and BRCA2 are genes that produce proteins to suppress tumours. When these are mutated, DNA damage can be caused and cells are more likely to become cancerous.
The mutations are usually inherited and increase the risk of ovarian cancer and breast cancer significantly.
When a child has a parent who carries a mutation in one of these genes they have a 50 percent chance of inheriting the mutations.
About 1.3 percent of women in the general population will develop ovarian cancer, this increase to 44 percent of women who inherit a harmful BRCA1 mutation.
Dr Gilbertson added: ‘This new research indicates the role of traffic-related air pollution in … increasing [the] incidence of breast cancer in the general population.’
BRCA1 and BRCA2 are genes – the breast cancer genes – which play a big role in preventing breast cancer by repairing DNA to stop defects leading to uncontrolled tumours.
Around one in 400 women inherit a BRCA mutation which puts them at much higher risk of breast cancer – famously, Angelina Jolie did and had a double mastectomy.
But the Stirling researchers say chemicals in traffic pollution can shut down the genes in the same way.
Dioxins, polycyclic aromatic hydrocarbons and aldehydes – all of which are found in exhaust fumes – are believed to stop the genes working.
Past research has confirmed this and the woman in the study did not have functioning BRCA genes but hadn’t inherited the defect.
And all the women’s cancers were early-onset (around half of cases are in women over 65), happened pre-menopause, and were recurring cancers.
Dr Gilbertson said: ‘We now have plausible mechanisms for inferring how the BRCA1/2 tumour suppressors in this highly-exposed border guard became dysfunctional and likely contributed to the ongoing epidemic of sporadic, early onset, premenopausal breast cancer among her colleagues.’
And shift work could make the pollution-cancer link worse, as past research on rats has shown those constantly exposed to daylight developed 60 per cent more tumours and the tumours grew 36 per cent faster.
The woman, whose case was revealed in a compensation claim at the Workplace Safety and Insurance Appeals Tribunal, was denied any compensation.
The research was published in the journal New Solutions.