An externality is a cost or a benefit that is not accounted for in the trade.
The massive number of COPD cases are not paid for when fossil fuels are burned. The good things we get from fossil fuels is why we pay for them, that's their value and it is accounted for.
If you think that those things are more valuable than what fossil fuels charge you right now, shouldn't you call up your utility and offer to pay more?
What sense of "value" are you using here? I like to live, so I find food to be a great thing, so perhaps in one sense the value of food is infinite, but in a much more useful sens of value I pay something that it much closer to the cost to provide it than how much I would theoretically pay if my choice were to go without.
Now recognize that this happens across all industries in the world every single day. New things are discovered that displace old things. We don't know all of the consequences for the new shiny product when we start producing and selling it to mass markets. Sometimes the new things have major disadvantages that we just don't know at the time we start using them. Look at historical problems with CFCs (which lead to ozone holes in the atmosphere) PCBs (which cause birth defects and can cause cancer), or how neonicotinoids impact insects (which can lead to the deaths of beehives). If the vendor pushing these products had to bear the full cost of the consequences of their use, they might never have been widely accepted. Capitalism is and always will be imperfect in this regard.