The US Food and Drug Administration (FDA) has taken more than 30 years to bring order to the sunscreen market and set standards to test the effectiveness of products. From 18 June 2012, sunscreens sold in the USA have to comply with new rules established by the FDA. They are required to be “broad spectrum”, which means that they must protect the skin against both UVA and UVB. In addition to this, they must also indicate the amount of time that they remain effective on protecting the skin. In addition, products with a sun protection factor (SPF) of under 15 must carry a warning that this is insufficient protection against skin cancer and those with an SPF over 50 may not claim that the product to be a “total sunblock”, because this concept is misleading.
Read further info here: http://www.thehealthyskinblog.org/sunscreens-whats-new-under-the-sun/