dangerousIt's dangerous to walk alone in the woods at night.
unsafeDon't play in the street - it's unsafe.
perilousA perilous journey through the mountains was their only escape route.
treacherousIce had made the roads treacherous.
harmfulPlease be aware that these chemicals are harmful to human health.
lethalThese medications can be lethal if they get into the wrong hands.
deadlyBelladonna can be made into a deadly poison.
riskySurgery at his age would be too risky.