I did some research and unfortunately no one's really certified their filters for arsenic, but I would go with Pur Plus filters.

Pur Plus and Zerowater seem to outperform Brita with heavy metals, although Lead and Mercury are really the only contaminants that overlap between the three. Zerowater isn't certified for as many heavy metals as Pur, although they say they've tested for arsenic reduction and achieved >99% filtration.

It's also good to know that Pur's faucet mounted filters are certified for a lot more contaminants than their pitcher filters