Physical Danger
Being a housekeeper is a physical job, so it stands to reason there's some physical danger to go along with it. Lifting, bending, and scrubbing can do a number on your back. Plus, there's a danger of slipping on a freshly mopped floor, even when you know first-hand that it's wet.
Learning the proper way to lift and having the right tools—like long-handled brushes to help you easily reach corners and high places—go a long way toward keeping you injury-free as you work. Watching out for stray toy trucks and pet toys is a good idea, too.
Another danger any housekeeper needs to be aware of is mixing cleaners. Mixing ammonia based cleaners with bleach based cleaners is a definite no no. Doing so creates a toxic gas and can put you in immediate danger (source).
A better idea? Make natural cleaning solutions using vinegar, baking soda, lemon juice, and borax, to name a few. You'll keep homes clean, fresh, and safe for the family that lives there, and for you, too. As an added bonus, you'll save money using natural solutions and will be doing the environment a favor.