Body Care
Map
Arrows point from what you learn first to what it opens. Point at a concept to light up its chain and where it comes back deeper. Right-click a concept (or press and hold it) for its lessons and stories.
- Proven to depth123
- Open
- Locked
- Comes back deeper
Learning path
In the order the concepts build on each other.
- Hearing protectionReadyLoud sound can kill the ear's hair cells, which never grow back in humans, so hearing loss from noise is permanent but preventable. Loudness is measured in decibels (dB): a conversation is about 60 to 70 dB, a concert about 94 to 110. Harm depends on how loud and how long: WHO puts 80 dB as safe for up to 40 hours a week. Keep headphones at no more than 60% volume, take breaks, and use earplugs in noisy places.
- Short sightReadyShort sight (myopia) makes far things blurry, usually because the eyeball has grown a little too long. It often starts in childhood and is becoming much more common. Fair tests in schools show that time outdoors, even in shade, helps stop it from starting; there is much less evidence that it slows short sight once it has begun. The evidence about screens and close-up work is mixed. Glasses fix the blur.
- Sun protectionReadySunlight carries invisible UV (ultraviolet) light that damages skin cells and causes most skin cancers, and much of it gets through cloud. When the UV index is 3 or more, shade and clothes protect best, with a hat, sunglasses that block UV, and SPF 30 or more on the skin you can't cover. Sunbeds raise the risk of skin cancer; a little sun is enough for vitamin D.
- Tobacco and nicotineReadyCigarettes, the qalyan (hookah) and most vapes deliver nicotine, a highly addictive drug. Tobacco kills more than 7 million people a year, over 1.6 million of them from second-hand smoke. The water in a qalyan doesn't clean the smoke, and an hour's session means much more smoke than one cigarette. Health agencies differ on how harmful vaping is, but agree that non-smokers and young people shouldn't start. Quitting helps at any age.
- Tooth decayReadyBacteria in plaque, the sticky layer on teeth, turn sugar into acid that dissolves the enamel and can make a hole. How often you have sugar matters a lot; brushing twice a day with fluoride toothpaste, spitting but not rinsing, protects the teeth. Untreated tooth decay is the most common health condition in the world.