Is it hazardous to live next to a cemetery?

Yes it is quit possible even if the coffins are placed in concrete tombs below the ground. The tombs are used to keep the coffin in place so they do not shift in soil yet the concrete is porous and therefore it allows rain water in and out which will slowly deteriorate the coffin allowing rust "from the coffin" as well as formaldehyde "used to preserve the body" to escape into water run-off. Bugs usually no longer consume bodies due to the presence of formaldehyde which essentially poisons the body and all viable nutrients the insects would otherwise have been able to utilize. hence why law enforcement can still exhume bodies "fully intact" to help forensics with old cases. In 1978 Congress ped a bill banning cemetery's from being placed within 1,000 yards of lakes, rivers, or streams due to poisonous leaching. who ever lives in these house no doubt has a purification system which protects those consuming the water supply but risks do still present themselves and yes depending on geographical sub-terrainian forms the water run off may be what fills their well after every rain. I would get the water tested by professionals directly from the well before it ever reaches the filters. then if any contaminates are found sue the builders of my home. the older the cemetery the more decomposition the coffins have suffered meaning the more body's you drink.