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Doctor's Consultation  by Dr. Iain Corness


WHO does it again?

If you want to attract some funding for your medical project, just mention the word “cancer” and get an item in the popular press and you’ve got your foot in the door.  You see, the popular media also likes the C word because it helps sell newspapers.

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.

What do you get in a blood test?

Patients do seem to get a little confused about “blood tests”. Your ‘usual’ blood tests do not test for “everything”. The reason for this is simple. There are so many tests that can be done, that testing would go on for weeks if you wanted “everything” checked. For example, the Australian Royal College of Pathologist’s Manual of Use and Interpretation of Pathology Tests that sits on my desk, lists 150 pages of tests that can be carried out. These include such items as a Reptilase Time, something I have never requested in 40 years of practice, or a red cell Galactokinase - ditto.

No, when we send you off for a blood test, we have to try and be reasonably specific, and sometimes even have to give the pathologists a clue as to where we are heading, and be guided by them as to some specific testing.

However, many times we are really just casting a ‘wide net’ to see what abnormalities we can turn up to use as a pointer towards the definitive diagnosis. One of the commonest is the “Complete Blood Count”, usually called a CBC, since we medico’s love acronyms, but remember this testing is in reality very far from “complete”.

The CBC does provide important information about the kinds and numbers of cells in the blood: red blood cells, white blood cells, and platelets. The CBC can help us evaluate symptoms such as weakness, fatigue, or bruising and even directly diagnose conditions such as anemia, infection, and many other disorders.

The CBC test usually includes the white blood cell (WBC) count as these cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells and normally fewer in number. When a person has a bacterial infection, the number of white cells can increase dramatically. There are five major kinds of white blood cells: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. The numbers of each one of these types of white blood cells give important information about the immune system. An increase or decrease in the numbers of the different types of white blood cells can help identify infection, an allergic or toxic reaction to certain medications or chemicals, and many conditions (such as leukemia).

The red blood cell (RBC) count is also part of the CBC. Red blood cells carry oxygen from the lungs to the rest of the body. They also help carry carbon dioxide back to the lungs so it can be exhaled. The red blood cell count shows the number of red blood cells in a sample of blood. If the RBC count is low, the body may not be getting the oxygen it needs. If the count is too high (a condition called polycythemia), there is a risk that the red blood cells will clump together and block blood vessels (thrombosis).

Another part is the Hematocrit (HCT). This test measures the amount of space (volume) red blood cells occupy in the blood. The value is given as a percentage of red blood cells in a volume of blood. For example, a hematocrit of 38 means that 38 percent of the blood’s volume is composed of red cells.

Hemoglobin (Hb). Hemoglobin is the substance in a red blood cell that carries the oxygen. The hemoglobin level is a good indication of the blood’s ability to carry oxygen throughout the body.

There is also the Platelet (thrombocyte) count, which is an important part of the CBC. Platelets are the smallest type of blood cell and play a major role in blood clotting. If there are too few platelets, uncontrolled bleeding may be a problem, such as occurs in Dengue Hemorrhagic Fever.

So even though the CBC does test for many factors, there are still another 149 pages of tests that can be done! If you want to know your blood group, or your HIV status, you have to ask for this separately! These are not the ‘standard’ tests, which are designed to assist us towards a diagnosis. So now you know!