more info on choosing a safe sunscreen/sunblock for children: UVA, UVB, what does it mean?

After my post on sunscreen the other day, I kept feeling like there had to be more to know so I kept poking around. Here's what I found:

• Katja at Skimbaco has a very helpful post up expressing her concerns about the ingredients in many sunscreens, a review of the various formulations, and some specifics on good sunscreens to choose...including some that are very reasonably priced. The Baby Blanket brand sounds almost too good to be true--pretty good choice of ingredients, waterproof, SPF 50, and at $12/9 oz it seems like a bargain. Baby Blanket also makes a number of other products such as a 'scalp spray' for bald babies and a lotion spray for legs and backs. I had kind of settled on the Aveeno Baby lotion for the big kids and California Baby brand for our infant, but I think that this would be a better all around choice. Anyway...
• The Skin Deep Cosmetics Database that I mentioned last time has a full listing of all the active ingredients in sunscreens, what their efficacy at blocking UVA and UVB rays is, what the potential harm in them is, and how bad it is for you (rated 1-10, very simple to follow). I won't even go over a few of the common ones since the information they provide is so complete and succinct.
  
• Safe Mama has created another handy cheat sheet distilling all this information into a handy list of good and bad choices in sunscreens. Print it out, shop with it, and feel like a good parent. They have a whole selection of other info sheets covering bath products, skin care, and sippy cups if you're interested.
  

Also, following the terminology can be a little tough, so here are a few terms to know:

• SPF: Sun Protection Factor. A measure of how effectively the sunscreen blocks the sun's UVB rays. It's calculated by comparing the amount of time needed to produce a sunburn on protected skin to the amount of time needed to cause a sunburn on unprotected skin.
  
• UVB: Short-wave part of the spectrum of sunlight; more potent than UVA in causing sunburn, thought to be the main cause of basal and squamous cell skin cancers as well as a contributor to melanomas.
  
• UVA: Long-wave solar rays. Less likely than UVB to cause sunburn, but penetrates the skin more deeply; considered chief cause of wrinkling and "photoaging." Apparently increases UVB's cancer-causing effects, but may be main culprit of melanomas. Not blocked by all sunscreens, so check the label!!
• Sunscreen: Chemically absorbs UV rays.
  
• Sunblock: Physically deflects UV rays.
• "Broad-spectrum Protection": This indicates that a product protects against UVA and UVB, but doesn't guarantee coverage against all UVA wavelengths. Sunscreens containing avobenzone, zinc oxide, or titanium dioxide should be effective against entire UVA spectrum.