system
Given the following post, respond as if you're commenting on Reddit:
human
How do carcinogens work?

How do carcinogens affect the body?

What compounds within food are carcinogenic?

Do carcinogens affect people differently?
gpt
1. Carcinogens are molecules that interact with a cell's system of checks and balances. Normally, our cells read DNA as a to-do list/recipe for carrying out all the necessary functions in order to keep us alive. And they're hella good at it. However, occasional mistakes are made during that process. Lucky for us, our cells have the ability to proof-read everything they do, as well as edit/correct the mistakes. Carcinogens, at various places along this process (depending on which carcinogen) hinder a cell's ability to proof-read or fix mistakes. Where normally a cell would realize that something is awry, a cell affected by a carcinogen would remain blissfully ignorant and carry on with its business.

Example: melanocytes are the cells that make you tan...they produce melanin, which helps block UVB radiation (side note: Gingers have trouble producing the proper kind of melanin, which is why they sunburn easily). UVB radiation is a carcinogen- that particular wavelength of light hits the chemical bonds in DNA molecules and causes the bonds to rearrange. Where you get into trouble is when that UV ray smashes the cell replication recipe... Normally, a cell reads the instructions and at the appropriate time, divides into two new cells. Then those cells just chill and do their job until it's their turn to divide. But sometimes when a carcinogen (such as UV radiation) messes up the instructions, those cells don't know they're supposed to chill. They just start dividing all over again. And since every cell gets it's entire DNA recipe book from its parent cell, the process continues to get passed down and it snowballs until you have a whole bunch of melanocytes that are multiplying like Duggars and don't know when to quit. We call that "Melanoma" in the biz.

2. Any molecule that has the ability to alter the structure of DNA is technically a carcinogen. You hear about "free radicals" and "antioxidants" in health food and supplement commercials... Free radicals are just molecules missing one electron/have one electron too many, and desperately want to gain/lose an electron to become stable. When free radicals run into DNA, they steal an e- or drop one off, which forces the DNA molecule to rearrange, starting that whole Bad-Recipe story over again. Antioxidants are molecules that join up with free radicals to stabilize them before they run into DNA somewhere and cause trouble. A couple other notable carcinogens in food are nitrites, found in smoked/barbecued meats, and alcohol (surprise!).

3. No, but yeah. Everyone's cells and DNA works the same way. Every cell in every person is potentially susceptible to carcinogens. However, since everyone's genes (recipes) are a little different, some people have higher tendencies for mistakes... Since Gingers struggle with melanin production, they don't can't block as much UV radiation, and are therefore more likely to get skin cancer (e.g., melanoma).  

TL;DR: carcinogens are mischievous little molecules that interfere with our cells' ability to regulate functions and repair defects.