possible reasons for death & injury:
accidents - a constant number of deaths & injuries by the population (could be adjusted so its more likely in youths); these are just deaths & accidents that just happen regardless of what you do, like stepping on legos or tripping down the stairs or slipping in the shower
reckless accidents - accidents that can have contributing factors such as businesses cutting corners with safety due to lack of money and causing workplace injuries, reckless driving accidents caused by lack of police presence and low education & high crime, regular car and house fire accidents caused by uneducated people due to lack of education
weather related accidents - caused by lack of road maintenance, lack of streetlights, lack of shelters and bad weather preparation but also uncontrollable factors like storm damage and fires caused by wildfires (im not gonna go into it in this suggestion but there should be policies that you can do to better enforce construction of homes to withstand natural disasters and fires)
dr#g overdoses - caused by homelessness, unemployment and not enough welfare options
s##cides and s##cide attempts - caused by low happiness and lack of entertainment and parks in the area and lack of welfare & hospital options
m##der and g#ng activity - caused by lack of police as well as lack of welfare options and unemployment/unhappiness all mixed together
alc#hol poisoning - caused by low happiness and lack of welfare options
preventable medical emergencies - caused by low funding in healthcare and not enough welfare options (more for old people) and pollution
old age - just the normal old age, where your body shuts down just because it can't be prevented
by all means, adjust this to what you want, this is just a suggestion