Seven out of 10 dry shampoos still on grocery store shelves contain detectable levels of a cancer-causing chemical — despite recent recalls of dozens of popular brands. Research by a laboratory in tested a random sample of 148 different products sold in CVS, Walgreens and by online retailers like Amazon across the country. Some 70 per cent were positive for benzene, a known carcinogen which is strongly linked to leukemia and other blood disorders.Among those that contained the chemical were drug-store brand favorites Batiste and Not Your Mother’s — alongside premium brands Pureology and Kerastase. Benzene levels varied by bottles, but nine were found to have at least 10 times…