Wikipedia can be your friend:
"When CO2 dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO−3) and carbonate (CO2−3). The ratio of these species depends on factors such as seawater temperature and alkalinity.
"Dissolving CO2 in seawater increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH."
CO2 in water is actually a weak ionic species because the bond with water is more covalent (electrons being shared to satisfy the “octet rule”). In large quantities of water carbonic acid is more than likely to remain in equilibrium with its surroundings greatly nullifying any potentially adverse effect in pH. These are proven scientific facts which the EPA is going to have to deal with and will get shot down.