Although sharing used needles is a high risk for HIV transmission, substance abuse and HIV goes beyond the issue of needles. People who abuse alcohol, speed, crack cocaine, poppers or other non-injected drugs are more likely than non-substance users to be HIV positive and to become seropositive. People with a history of non-injection substance abuse are also more likely to engage in high-risk sexual activities. Many injection drug users (IDUs) use other non-injected drugs primarily. When an IDU is HIV-positive, needle sharing may be the primary risk factor, but other non-injected drug use may have a great effect on risk behaviors. For example, a study of high risk clients in a methadone treatment program found that those at highest risk for HIV infection were also crack cocaine users. A survey of heterosexuals in alcohol treatment programs in San Francisco, CA, found HIV infection rates of 3% for men who were not homosexually active or IDUs and 4% for women who were not IDUs. This was considerably higher than rates of 0.5% for men and 0.2% for women found in a similar population survey. In Boston, MA, a study of gay men found a strong relationship between use of nitrite inhalants or “poppers” and HIV infection. Men who always used poppers while engaging in unprotected anal sex were 4.2 times more likely to be HIV positive than men who never used poppers and engaged in unprotected anal sex. Crack cocaine use has been shown to be strongly associated with the transmission of HIV. A study of young adults in three inner-city neighborhoods who smoked crack and had never injected drugs found a 15.7% HIV rate. Women who had recently had unprotected sex in exchange for money or drugs, and men who had anal sex with other men were most likely to be infected.