dangerousIt's dangerous to walk alone in the woods at night.
unsafeDon't play in the street - it's unsafe.
hazardousHeavy rain is causing hazardous driving conditions.
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.
deadlyBelladonna can be made into a deadly poison.
riskySurgery at his age would be too risky.