some metals are, though there isn't much of those metals in used oil. aluminum or steel won't hurt the earth much, if at all. i'm thinking in terms of the solids that a filter collects - petroleum sludge particles, soot, and whatever chemicals form when you mix partially burned gas/oil mixture.How are tiny metal shards more harmful than oil?
Oh, I usually just trash mine, I never thought to recycle the filter!
The biggest contaminate other than the residual oil may be lead for which there is no safe level, especially for children. Landfill design has gotten pretty good but it's still not if they leak, but when. Another overlooked pollutant from landfills is the leachate. All landfills have to collect accumulated rain that leaches through the waste to the bottom which is pumped to holding tanks. The leachate is usually considered hazardous. In our county it's sent to the local wastwater handling plant which "treats" the waste then spreads the residual (sludge) on farmland. There are many contaminates in sludge that get washed off the farmland and into surface waters. That's why there is good evidence of pharmaceuticals in drinking water. What goes around comes around.some metals are, though there isn't much of those metals in used oil. aluminum or steel won't hurt the earth much, if at all.