How many times have you read “breakthrough” as regards some form of cancer treatment (which will require another five years of expensive testing)? How many times have you read items that claim something disastrous will happen to you by using something that is part of our lifestyles? Be that mobile phones causing sterility and coffee increasing cancer somewhere.
Here’s the latest. Exhaust from diesel engines causes lung cancer, a World Health Organization (WHO) agency said this month, citing a review of studies. Baht busses to grind to a halt on Beach Road?
Diesel exhaust also was linked to an increased risk of bladder cancer, said the International Agency for Research on Cancer, based in Lyon, France. The group published the findings after a review over eight days by a panel of scientists. An earlier review, in 1988, classified diesel engine exhaust as “probably carcinogenic.”
Hundreds of years ago, a very smart doctor called Paracelsus came up with the observation that “dosage alone determines poisoning.” This was a real breakthrough. To poison someone, there was a certain dose necessary for this to happen.
Lots of reasons for this. With human beings there is a characteristic we all have called ‘homeostasis’. This is where the body will try to return itself to its original condition. In other words, repair itself. Broken bones mend, lungs will expel foreign material and livers even regenerate themselves. Provided the rate of repair is faster than the rate of destruction, the body will be fine. However, if the rate of destruction exceeds the rate of repair, then you are in trouble.
There is another factor to be aware of - and that is ‘time’. Dose is amount divided by time. Simply, 10 gm given over one hour is ten times the dose of 10 gm given over 10 hours. This was how the poison arsenic was considered a tonic at low dosage, but was a fatal poison at high dosages. Dosage alone determines poisoning, thank you Paracelsus.
Now let’s get back to the shock-horror headlines that exhaust from diesel engines causes lung cancer. It probably does, but at what dose? How many of us are subjected to diesel exhaust 12 hours a day, for example? I suppose a baht bus driver might be, but it would be rare. Most are parked at the side of the road for at least six of the 12 hours in their shift. Do our diesel baht bus drivers have more lung cancers than anyone else around here?
But, remember that according to the WHO, cancer killed 7.6 million people worldwide, and was the leading cause of death globally in 2008, the most recent year available. Lung cancer was the most lethal type, and accounted for 18 percent of all cancer deaths, the agency said.
Common sense would tell you that carcinogens that attack the lungs need high dosage to do their destructive work. We have your exposure to baht bus fumes (diluted in the air remember) for perhaps 20 minutes a day while crossing Second Road several times. For those of you who are smokers, the known carcinogen cigarette smoke (undiluted) is in intimate contact with the lung tissue for two hours a day (20 cigarettes at six minutes each). Common sense (and Paracelsus) might make you think that cigarette smoking is a more likely cause of lung cancer than baht busses.
Now, getting back to the WHO agency and diesel exhausts, “The scientific evidence was compelling and the working group’s conclusion was unanimous: Diesel engine exhaust causes lung cancer in humans,” said Christopher Portier, chairman of the IARC working group. However, the agency is not providing guidelines on what level of exposure is carcinogenic, leaving it up to national and international regulatory authorities to weigh their own conclusions, according to Christopher Wild, director of the agency.
So they have implicated diesel exhausts, but will not provide guidelines for exposure. I smell a rodent rather than diesel fumes.