Rytek book is talking about nitrates.
I did a quick search and found this on another forum. This was not 100% right, however. I did have to correct a couple numbers but basically, most cheese does not have a high enough water activity level to allow botulism to grow
"First, I always say you need to prepare and cook your food at your own comfort level. Though Rytek's statement sounds practical, I'm not sure how sound it is. Rather then say I've never gotten sick cold smoking vegetables /or cheese, I did a quick search on the USDA and FDA sites and did not find any warnings on cold smoking vegetables or cheese. Though I will continue to research this.
Clostridium botulinum, the bacteria that which produces botulism in foods, needs a pH of 4.6 or higher, ideally 6. I haven't checked out the pH of most cheese, so I can't confirm that most cheese pH is lower than 5. The only cases of botulism I could find for cheese is a rare case that occurred in cottage cheese, and cases involving cheese sauce.
Other then a food source; water is very important for an environment to grow. Food may have water (moisture), but not all that water is available for bacteria to use. In foods, part of the water is bound tightly to the molecules of the food, preventing it from being used by bacteria. The amount of water available for bacteria is called Water Activity or Aw. This is not a measurement of the amount of water in the food, but the amount of water that is available to bacteria. Aw is measured on a scale of 1.00 as pure water, to 0.00 as bone dry. Meat and fish are rated as 0.99, hard cheese is rated at 0.85; and I am still researching the Aw of most common vegetables. Different bacterias require different minimum amount of Aw to exist and grow. Clostridium botulinum requires an Aw of at least 0.94; therefore in hard cheese there is not enough Aw to create a favorable environment, for this bacteria to grow."