Tuesday, July 18, 2023


 All right there is good info on line and there is ridiculous bullsh*t information on line. O.K. that may apply to almost all subjects. How do you know for sure when you are reading bullsh*t? Simple, read carefully and take note of internal contradictions within the article. For example if an earlier sentence refers to low bitumen content in coal tar and four sentences later the same article states that coal tar's primary constituent is bitumen then you should be on high alert. If an article suggests that coal tar has high concentrations of PAHs (polycyclic aromatic hydrocarbons) and asphalt has none and then again a few pages later amends their statement to say well coal tar has high concentrations of PAHs and asphalt has low concentrations then again something may well be amiss.

 To date I have likely read at least a couple of dozen publications dealing with coal tar paving (i.e. macadam) versus asphalt paving. While the production of each is different as well as from a somewhat different source in that coal tar comes from coal and is a by-product of the production of coal gas whereas asphalt is both a natural product found in some areas of the world it is more commonly produced from petroleum using a distillation process. Either way however the chemical constituents are extremely similar. 

Keep in mind that petroleum (crude oil) is produced via carbon based lifeforms including vegetation and very small animal life which under high pressure and heat from deep burial over eons turns into crude oil and gas. Also coal is produced from wood (trees) which are a form of vegetation which also has been subjected to high pressure and temperatures over eons of time. Their chemical basis is hydrocarbons which simply stated are hydrogen and carbon molecules. Yes asphalt has a few additional molecules including sulfur, nitrogen and oxygen.  

Some of these studies measure the concentrations of chemicals in water runoff from asphalt driveways versus coal tar paving (i.e. macadam). Most articles however have focused on the sealants later used on these forms of paving. The asphalt sealers (put on with a large brush from out of a can) have an extremely lower concentration of toxic chemicals than the coal tar sealers also applied with a large brush on top of a paved driveway or parking lot.  The issue to date does not remotely seem to be the type of paving used (coal tar macadam) versus regular, normal asphalt paving. The issue is the surface sealer sold and applied later to allegedly smooth, preserve and darken the pavement back to it's original colour. 

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