Almost all 3D printers have issues that could cause health problems.
FDM/FFF printers heat plastic to a temperature that may cause it to off-gas, and these byproducts may not be healthy.
SLA printers often use epoxies that may off-gas, or may be somewhat toxic prior to being cured.
Powder based printers can also off-gas, in addition to the powder itself presenting a possible hazard.
Many hobbyist and small companies dance around the problem, and suggest that the machines always be used in well ventillated areas. Professional machines often have filters and ventillation systems built in.
Rather than trying to find a "perfectly safe" 3D printer, spend some time deciding what you want to use one for, find printers suitable for your use, and expect that you'll need to provide reasonable ventilation for almost any printer. Plan your installation for that, and you should be able to make any printer safe for your required use.
If, however, you plan on setting up a printer farm with many printers, and plan to have yourself or others spend significant time operating them, I suggest you work with a health and safety professional and have them identify possible hazards and plan mitigation.
I would like to buy a 3D printer, but I'm concerned about the health risks that are associated with its operation. Some groups of scientists say it can be harmful for humans.
What do I need to consider before buying a 3D printer if I care about my health? Are there any safe printers?