Overview – The Chimney Downside: From Percival Potts to Archibald Leitch
Hyperlinks between occupational dangers and most cancers
Percival Potts has entered the favored epidemiological custom for offering one of many earliest hyperlinks between occupational exposures and particular cancers… particularly, scrotal most cancers in chimney sweeps. And, to be clear, it was squamous cell carcinoma of the scrotal pores and skin, not testicular most cancers. And what was each placing and stunning about his observations was the younger age of many sufferers.
The issue has an extended historical past. Chimney sweeps plied their commerce in Shakespeare’s time. “ To appear like him, they’re black chimney sweeps, ” he wrote in The work of affection is misplaced.
Appropriate prognosis of cancers
Nevertheless it was the introduction of tall, slim chimneys, in response to the Nice Fireplace of London in 1665, that turned out to be a turning level. Sadly, these chimneys tended to turn out to be clogged with soot: the chimney sweeping commerce took off. The younger boys have been co-opted to do the soiled work and a consequence for them was a legacy of poor well being – lung illness, dermatitis, pores and skin warts (recognized within the commerce as sooty wart) and scrotal pores and skin most cancers. .
Besides that earlier than Pott’s scrotal examination, cancerous growths have been thought-about venereal and finest handled with mercurials. He offered not solely an accurate prognosis, but additionally lots of sympathy for his younger sufferers.
Therefore Sir Percy’s lament: “The lot of those individuals appears singularly harsh; of their childhood, they’re most frequently handled with nice brutality, and virtually starved with chilly and starvation; they’re pushed into slim and generally sizzling chimneys (sic) the place they’re bruised and virtually suffocated: and once they attain puberty, they turn out to be notably topic to a illness of probably the most noisy, painful and deadly.
A very English illness
This most cancers continued by way of the 19e century and was acknowledged by surgeons and sweepers as a pledge of commerce. However then there was an anomaly. Scrotal pores and skin most cancers appeared to be a very English illness. Sir Henry Butlin, additionally at Barts, despatched assistants to scour Europe’s fireplace stacks to Germany, Holland, Belgium and France to seek for clues as to how foreigners escaped the soot penalty.
And the reply? Nicely, for the Germans it was apparent. They have been a lot better organized, washed extra often and wore protecting clothes. And regarded cool guys too. However relating to the French, Butlin did not maintain again, confidently saying it might solely be about cleanliness “which is completely inconceivable to anybody who is aware of the final habits of the French decrease lessons.”
Different variables that Butlin thought-about vital have been the construction of the chimneys and the quantities of soot in addition to the use, in England, of so-called arduous coal, whereas elsewhere in Europe, of coke, wooden and charcoal. have been used, producing much less soot residue.
The hyperlink between soot and pores and skin most cancers
Which brings us to the query: what does soot trigger pores and skin most cancers? This may take us to the early days of ICR in its Chelsea labs – however earlier than we get there, this is one other conundrum. Contemplating that chimney sweeps, even in my youth, have been lined in soot everywhere, why was the scrotum the hotspot for most cancers?
On the finish of the 19e century it started to emerge that there have been associations between occupational publicity to shale, pitch and tar oils with pores and skin most cancers, together with scrotal most cancers. There was clearly one thing very doubtful in regards to the carboniferous combustion. In 1922, an examination of 141 males in Manchester with scrotal pores and skin most cancers made the shocking discovery that just one was a sweep, however 69 spinning machines or mules have been working within the Lancashire cotton business. Solely males occupied this place and lots of of them began on the age of eight. The mules have been lubricated with unrefined oil and the employees, scantily clad in cotton trousers in sizzling environments, leaned towards the mules have been encrusted with oil “between the higher thighs and the stomach”. And on this cavalier English means, there have been no washing services.
Why scrotal most cancers?
Now we’re getting nearer. It is time to name on Archibald Leitch, director of the Analysis Institute on the Royal Most cancers Hospital in Chelsea, aka ICR. He had calculated the chances of sweepers or mule drivers dying from scrotal most cancers to be 1 in 1,400 and 1 in 2,000 per 12 months respectively. However why the scrotum? Leitch advised it was a mixture of warmth and secretion-dissolving properties from the sebaceous glands making the pores and skin extra absorbent and susceptible to the entire dangerous chemical compounds in soot, oils, and tar. I’ll purchase this as a solution.
The invention of benzo (a) pyrene
So the place is that this path of soot tar main us? Nicely, in truth, in 20e century of experimental most cancers science and the primary mechanistic insights into most cancers. Leitch’s successors and the primary inhabitants of the ICR laboratories in Chelsea have been natural chemists and their path got here from Japanese scientists – who in 1915 induced pores and skin most cancers on the ears of rabbits by portray over tar of coal. This offered an essay to ask the query: what does soot and tar trigger pores and skin most cancers? The reply offered by Ernest Kennaway and his colleagues at ICR within the early Thirties was a category of chemical compounds known as polycyclic fragrant hydrocarbons, or PAHs, considered one of which, benzo (a) pyrene was notably potent. Which in flip led some 30 years later to Peter Brookes and Philip Lawley’s historic discovery at ICR that PAHs like benzo (a) pyrene induced most cancers by straight binding to DNA and mutant.
It might have and maybe ought to have been much more revealing. Kennaway and his colleagues, observing that cigarette tar would include benzo (a) pyrene, requested if this might clarify lung most cancers, the incidence of which was beginning to enhance within the Thirties. Right here is the unusual factor; nobody appears to have observed. When Richard Doll started his landmark epidemiological research of lung most cancers within the Fifties, I doubt he heard of benzo (a) pyrene; He suspected that automotive exhaust fumes have been the reason for lung most cancers. This isn’t to decrease Doll’s accomplishments, nevertheless it illustrates how alternatives may be simply missed. However then why did not the scientists at IC run with this concept?
The path of soot
Quick ahead to 21st century and genomic sequencing reveals distinctive signatures within the DNA of most cancers cells of chemical carcinogens comparable to benzo (a) pyrene. The case is closed. The soot path is basically forgotten, nevertheless. However we owe a debt to Percival Potts and his successors, together with Archibald.
And let’s all hope that Santa is carrying some actually thick pants this Christmas.
NOTE A part of the above piece was taken from my e-book ‘Most cancers, the evolutionary legacy ‘. Oxford College Press 2000.