Two kiosks for the disposal of medical needles have been installed in Malden by the city’s Board of Health. One kiosk was installed at the city’s senior center at 7 Washington St. and is available only during business hours. The other, located at 630 Salem St., is available for use 24 hours a day. The doors on the kiosks shut like a mailbox, preventing needles from being removed after they are deposited. The office of the Board of Health at Malden Government Center also accepts needles for disposal.