I personally use ProCoco coconut husk and it has been great!

I met them a while back at a reptile show and ended up buying 10 bricks since they were having a sale. Half a brick is enough for a full change my AP T8, T10 and T12 enclosure. Each brick retail is $12.50 so I think that's a pretty cheap solution and they're available on amazon and other site. I attached a link just in case: https://www.arbico-organics.com/prod...sting-supplies

Even though there might not be specific studies regarding pine, it just doesn't make sense to risk you pet's health to save a few bucks.