Do cosmetics containing sunscreen provide adequate sun protection?

I was thinking of buying a face powder that says it has an spf of 30. It seems convenient to have a powder sunblock since lotions make my oily face greasy. However, I was wondering if this powder will even be effective as a sunblock since I heard that some moisturizers and other products that advertise an added SPF sometimes don't have a high enough concentration of sunblocking ingredients to make it effective. I would like to know what do you think before I make my purchase.


Where can I find the birth control sponge and what’s the efficacy rate?

1) I've always used condoms combined with a sponge for birth control. That worked well because if anything happened with the condom, there was always a backup — it made me feel safer. Then I get to New York, I go into three drug stores, and none of them have sponges. Now what? I don't want to rely on just condoms, I don't want to take pills because the whole hormone thing is rather frightening, and a doctor said that diaphragms make you more prone to get urinary tract infections, which I get frequently. So what am I supposed to do? What's up with this total absence of sponges?

2) In exploring other forms of contraception, what is the reliability rate of the "sponge"?