Tuesdayâs debate between the Democratic presidential candidates, including Hillary Clinton and Bernie Sanders, will be streamed online for free. CNN, which is hosting the debate, will have it available on CNN.com and on the networkâs mobile apps. Coverage begins at 8:30 p.m.
Paraphenylenediamine (PPD) is a chemical substance that is widely used as a permanent hair dye. It may also been found in textile or fur dyes, dark coloured cosmetics, temporary tattoos, photographic developer and lithography plates, photocopying and printing inks, black rubber, oils, greases and gasoline.
A PPD test involves injecting small amounts of protein from the mycobacteria that cause tuberculosis into the skin. PPD stands for 'purified protein derivative', indicating that the substance injected is non-infectious. This is known as the Mantoux-method TST (tuberculin skin test) . PPD is only recommended in people who have not had a prior positive test. It should be repeated annually in anyone who is at high-risk of acquiring TB.