Glad you asked!

In Ontario Canada the asphalt mixes are designed in laboratories and must meet a number of standards to be an allowed mix. One of those requirements is its ability to resist "leaching" or contamination of the surrounding environment. This is accomplished using additives that ensure the product remains bound to the granular particles in the mix. Also the oils used are rated upon their temperature sensitivity. In Ontario the standard is 58-28. Which means they are at good performance when within the temperature range of 58 degrees Celsius and -28 degrees Celsius.