Business Green: Democrats pushing for the proposed Waxman-Markey bill to be approved by the Senate could soon have an important new bargaining chip, after the head of the Environmental Protection Agency (EPA) signalled this week that it would soon formally declare that carbon dioxide constitutes a dangerous pollutant. The long-awaited decision was trailed back in April when the EPA released an “endangerment finding” for public review, which ruled that carbon dioxide and six other greenhouse gases …