McFarland owns a house on the canal in Avalon Manor.
The court document indicates he used a small boat docked behind the house to take the waste out and dump it.
Detectives used serial numbers on the waste that washed up to narrow their search to 13 dental practices on the east coast.
McFarland's was one of them.
No criminal charges have been filed against Dr. McFarland, despite the confession described in the court document.
Why anyone would do it remains a mystery. Other dentists tell Action News that it costs them only about $75 a month to get rid of their medical waste products.
The needles and other waste forced Avalon to close several beaches in the days leading up to the Labor Day weekend, and left vacationers afraid to go near the water.
McFarland's neighbors in Wynnewood say they're stunned. They say he's a good dentist with a sterling reputation.
"I was appalled," said neighbor John Ruggero. "Completely disgusted and appalled that anyone of any stature would do that, let alone an educated person."
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