Lisa’s Answer

I recommend Two Sisters Ecotextiles.  All of their products are free of harmful chemicals.  You can contact them and find out if their upholstery fabric is durable enough for truck seats.  Leather is very durable but can be processed with hundreds of chemicals.  You can read more here about the chemicals in leather, natural leather, and sythetic leather.  There are vegetable tanned leathers that aren’t as chemically intensive, but you would need to find out what chemicals are used in the specific leather you are considering.

It’s also worth noting that the cushioning under the fabric is probably a bigger exposure than the cover.  The foam degrades over time and can release toxic dust.  Unfortunately, the fabric will not mitigate the exposure.  If you are re-covering your seats anyway, consider replacing the foam cushioning with natural latex.