Almost ten years ago, I wrote a feature article on the cancer risk associated with the bracken toxins known as ptaquiloside for ChemWeb. The article was updated and mirrored on Paul May’s Molecule of the Month website at Bristol University, and quite bizarrely still draws a few readers to the Sciencebase site via my byline on the article. I suppose the reason it is still popular is that it makes it to page on in Google should you search for the word bracken.
Anyway, this article occasionally triggers some rather interesting correspondence with readers. Most recently, John Nayler emailed me to ask whether or not toxic chemicals from bracken might leach into groundwater beneath bracken-infested areas. I had to admit I did not know, but a paper published recently in the journal Chemosphere (2007, 67, 202-209) discusses the microbial degradation and impact of ptaquiloside on soil microbes themselves, which sheds some light on the potential impact of this carcinogenic toxin.
Another of Nayler’s concerns regards whether or not bracken is not simply an unpleasant weed with a cancer risk associated with eating the “fiddle heads” (a delicacy in Japan), but whether or not landowners, whose land is infested with bracken might be liable for public health lawsuits should those with a right to roam on their land be exposed to bracken spores. The risk may be small but that never stopped an ambulance-chasing lawyer in the past.
Cancer Research UK has a FAQ on the cancer potential of bracken. Despite isolated ptaquiloside coming up positive in carcinogenicity tests a decade ago, the latest research, according to Cancer UK is that there is no risk of cancer associated with eating bracken fiddlehead greens. So, what about those spores. Studies have shown bracken spores to cause cancer in mice, but those mice were given a lot of spores and to extrapolate to human cancer risk is (death)wishful thinking. A walk among the bracken is more likely to trigger a sneezing fit if the spores are high than anything else, and as CRUK points out, diet and smoking are far greater risk factors than bracken for cancer.