When I wrote this post I didn't know that I was living in an apartment with an improperly vented water heater in my bedroom for 3.5 years. So, not only was I most likely breathing carbon monoxide, I was also potentially breathing all of the other contaminants that are created with combustion while I slept. Some of the other contaminants are listed here:
"Carbon monoxide poisoning can cause damage which impacts cellular functioning throughout the brain and body. It deprives cells of oxygen and has a toxic effect. The brain, nervous, and endocrine systems are especially sensitive to oxygen deprivation and toxic exposure."
(Quoted from: http://www.carbon-monoxide-survivor.com/carbon-monoxide-poisoning-endocrine-d...