The claim that used needles from individuals with substance use disorders carry high levels of microbial and viral contamination is a matter of everyday observation and established biomedical fact, requiring no formal citation.
The claim refers to the well-established biological reality that used injection equipment harbors bloodborne pathogens and environmental microbes. Because this is trivially true and a matter of direct observation in medicine and public health, it falls under the COMMON_KNOWLEDGE category as per STEP 0, and no paper citations are necessary.