The syringes were discovered in a beach-side waste bin inside a thin supermarket plastic bag at Fort Island in the Parish of Malew. None of the syringes were in boxes and a large number still had needles uncovered.
The incident has led to a part-time member of Beach Buddies’ staff having to undergo a course of powerful antibiotics and anti-HIV medication as a precaution advised by doctors.
Bill Dale, the founder of Beach Buddies, said: 'It beggars belief that the person who did this could possibly think this is acceptable.
'Leaving dozens of used syringes with needles exposed in a plastic bag in a public rubbish bin is something beyond the understanding of any normal person.
'What was going through the brain of the person who did this? It is stupidity and irresponsibility beyond belief. This not just careless, this is a totally irresponsible action which is absolutely unacceptable.'
A spokesperson for the charity said: 'Beach Buddies occasionally find single syringes on beaches, and the charity always gives a safety talk about finding items like this before every volunteer session.
'But to find over 50 syringes in a plastic bag with many of them having needles exposed is just wrong on every level.'
Police have been informed about the incident, with enquiries focused on a label found inside the plastic bag with the name and address of a local person.