Clean Harbors Inc (NYSE:CLH), the leading provider of environmental, energy and industrial services throughout North America, today commented on the April 24, 2014 filing of a Schedule 13D by Relational Investors, LLC (“Relational”), which stated that Relational owns 9.08% of Clean Harbors’ common stock.

Clean Harbors

Chairman and Chief Executive Officer Alan S. McKim, said, “Clean Harbors has a long history of transparency and open communications with shareholders. Our Board of Directors and management team are committed to building long-lasting value for all of Clean Harbors Inc (NYSE:CLH) shareholders and we welcome their investment in the Company.”

“Clean Harbors has a proven track record of delivering value to our shareholders. In fact, over the past decade, our stock has outperformed the S&P 500 by more than 12 times during that timeframe. Led by our management team, we have achieved our outstanding long-term performance through a combination of targeted acquisitions and steady expansion through organic growth.”

“In the past two months, we have held positive discussions with Relational. Their investment in Clean Harbors demonstrates their agreement with us that there is additional value in our Company. We agree with Relational’s statements regarding our strong position in the hazardous waste market and their endorsement of our plan to continue to invest in capacity expansion in these businesses. Relational supports our efforts to expand our margins and improve asset utilization to create superior equity value. We are closely aligned with that viewpoint as we continue to work toward our previously stated long-term objective of achieving 20% Adjusted EBITDA margins.”

About Clean Harbors

Clean Harbors Inc (NYSE:CLH) is North America’s leading provider of environmental, energy and industrial services. The Company serves a diverse customer base, including a majority of the Fortune 500, across the chemical, energy, manufacturing and additional markets, as well as numerous government agencies. These customers rely on Clean Harbors to deliver a broad range of services such as end-to-end hazardous waste management, emergency spill response, industrial cleaning and maintenance, and recycling services. Through its Safety-Kleen subsidiary, Clean Harbors also is North America’s largest re-refiner and recycler of used oil and a leading provider of parts washers and environmental services to commercial, industrial and automotive customers. Founded in 1980 and based in Massachusetts, Clean Harbors operates throughout the United States, Canada, Mexico and Puerto Rico. For more information, visit www.cleanharbors.com.

Safe Harbor Statement

Any statements contained herein that are not historical facts are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements are generally identifiable by use of the words “believes,” “expects,” “intends,” “anticipates,” “plans to,” “estimates,” “projects,” or similar expressions. Such statements may include, but are not limited to, statements about future financial and operating results, and other statements that are not historical facts. Such statements are based upon the beliefs and expectations of Clean Harbors Inc (NYSE:CLH)’s management as of this date only and are subject to certain risks and uncertainties that could cause actual results to differ materially, including, without limitation, those items identified as “risk factors” in Clean Harbors’ most recently filed Form 10-K and Form 10-Q. Therefore, readers are cautioned not to place undue reliance on these forward-looking statements. Clean Harbors undertakes no obligation to revise or publicly release the results of any revision to these forward-looking statements other than through its filings with the Securities and Exchange Commission, which may be viewed in the “Investors” section of Clean Harbors’ website at www.cleanharbors.com.

CONTACT: Clean Harbors, Inc.

James M. Rutledge, 781-792-5100

Vice Chairman, President and CFO

[email protected]

or

Jim Buckley, 781-792-5100

SVP Investor Relations and Corporate Communications

[email protected]