US stocks took their biggest loss in almost a month on Tuesday as investors worried about the health of the US economy and sold shares in retailers and car companies, the AP reports. Machinery companies also fell and the price of oil continued to decline. Royal Caribbean fell more than 6% after the cruise operator lowered its guidance. Oil reversed early gains to close down 1.4% at $39.51 a barrel in New York, the first time US crude closed under $40 since April. The Dow Jones industrial average closed down 91 points, or 0.5%, to 18,314. The Standard & Poor's 500 index fell 14 points, or 0.6%, to 2,157. The Nasdaq composite slid 46 points, or 0.9%, to 5,138. (More Dow Jones stories.)