system
Given the following post, respond as if you're commenting on Reddit:
human
How are the harmful levels of toxicity in cigarettes regulated today compared to the 40's, 50's, etc.. Have cigarettes gotten more or less dangerous at all?

Just wondering how companies decide what and how many dangerous chemical materials they are allowed to use in cigarettes. Do they generally just put whatever they want in them?
gpt
In the fifties cigarette companies started experimenting with chemicals that would make cigarettes more addictive and more 'satisfying' like flavours etc.
The most successful additive in terms of addiction was ammonia, which increased the bioavailability of nicotine. Since this addition, cigarettes have become more pathogenic... This is reflected in the comments people make about their great- grandfather who smoked 40 cigarettes a day and died of old age at 97 or something. This doesn't tend to happen today- we know now that smoking kills up to 50% of smokers from all kinds of disease, with some studies suggesting more.

The level of carbon monoxide and particulate pollution inhaled is entirely dependent on the smoker's individual smoking style which renders filters of any kind useless. A person who is heavily addicted to nicotine will self titrate from whatever delivery mechanism they are using regardless of filters (depth and frequency of 'puff') 

Edit: death rate amended by request (credit to Mfukar)