Arsenic can leach to the surface of the treated wood, becoming accessible for absorption through exposed hands and skin touching the wood surface and, especially in the case of children, ingestion through normal hand-to-mouth behavior. […]

Exposure to arsenic can cause cancer of the lung, bladder, skin, kidney, prostate, and nasal passage. Data released in November 2003 by the U.S. Environmental Protection Agency (EPA) show that 90% of children repeatedly exposed to arsenic-treated wood face a greater than a one-in-one-million risk of cancer.

https://nchh.org/information-and-evidence/learn-about-healthy-housing/health-hazards-prevention-and-solutions/arsenic-treated-wood/

Sounds like a great pipe :D

My town set up log fencing along our trails and sidewalks. They would decay so fast, the ranger would have to drive by everyday to check the fences.

They treated the fence the same way you described. They were always tinged green. Kids would run their hand down it, on their way home. Enough kids got sick, that the town noticed.

Did they take down the rotting, poisonous fence?

Nope; everyone just knows not to touch it. They really like that “rustic” look.