The Teamsters have hurled the latest salvo in the battle over the nation’s trash.

The Teamsters sent letters to major institutional investors in the three largest U.S. solid waste companies — Waste Management, Allied Waste Industries and Republic Services, asking for assurances that they would meet fiduciary obligations as they face competing financial interests.

Here’s the situation.

Waste Management, the largest U.S. trash hauler, has bid for Republic, the third largest. Republic has agreed to buy Allied Waste, the No. 2 hauler. But Republic has rejected the Waste Management bid.

The Teamsters say the situation raises questions as to how investors with significant stakes in each of the companies will manage potential conflicts of interest and act in the interests of their clients, which include many pension and benefit funds connected to the Teamsters.

Others have jumped into the mess as well, although for other reasons.

Bill Gates’ investment arm asked Waste Management to drop its unsolicited $6.2 billion bid for Republic, calling it “ill-timed and poorly conceived.”

“An acquisition of Republic will most certainly burden the company with excessive debt, distract your management, result in significant regulatory burdens, and thereby reduce shareholder value,” it said.

Waste Management has maintained that its bid for Republic was in the best interest of both companies and its stockholders.

(Photo credit: Reuters)