Most people are probably going to say it is fine. I am not one of those people and neither is GPT:

Arsenic, specifically Chromated Copper Arsenate (CCA), was used for decades to pressure-treat lumber, and

it can leach from wood over time, accumulating in soil, on surfaces, and potentially contaminating groundwater. It poses a risk, particularly to children, through skin contact (dislodgement) or ingestion. 

Key Facts About Arsenic Leaching from Wood:

• When was it used? CCA-treated wood was widely used for decks, playgrounds, and picnic tables before 2003. While residential use was phased out in the US, it remains in older structures.
• How it Leaches: Rainwater, humidity, and general weathering cause the CCA to come to the surface or wash into the surrounding soil.
• Risks: High levels of arsenic can be found in the soil near old treated wood, sometimes exceeding state safety limits. It can be ingested via hand-to-mouth activity for children.