Clean Harbors Updates Participation in Gulf Oil Spill Response

Norwell, MA – May 18, 2010 – Clean Harbors, Inc. (“Clean Harbors”) (NYSE: CLH) reported today that as the leading provider of environmental emergency response services in North America, the Company has been contracted to provide a variety of environmental response services throughout the Gulf of Mexico region to protect the area’s natural resources from the effects of the ongoing oil rig spill.

Clean Harbors currently has deployed a large number of its own personnel and subcontractors to a variety of locations throughout the Gulf. As part of its engagement, it also has been tasked with recruiting and training residents of the affected Gulf areas to safely conduct oil spill clean-up along the coastline. Clean Harbors has been contracted by government agencies and private organizations to provide a wide range of support and logistical services. As part of its efforts, the Company is supplying equipment, including boats, containment boom, skimmers, and vacuum trucks, as well as recovery and treatment systems from its extensive equipment inventory. Clean Harbors is involved in many aspects of the spill response including containment, removal, disposal and recycling of the recovered oil.

“While the full scope of our participation in the clean-up efforts continues to evolve, we are providing this update on our activities in response to numerous inquiries from the media, investors and other stakeholders,” said Alan S. McKim, Chairman and Chief Executive Officer. “Our customers’ requirements will depend upon weather, tidal conditions and the amount of oil that ultimately strikes the coastline. Therefore, the duration of our contracts, staffing levels and dedicated equipment are subject to frequent change. However, we believe we have reached a point where we can quantify the potential near-term revenue impact from the spill.”

“At this time, we are estimating that this event will result in an increase in second quarter 2010 revenues of 15 to 20 percent of the current First Call consensus estimate of $352.0 million,” said James M. Rutledge, Chief Financial Officer. “Due to the fluidity of the situation, we do not anticipate providing any further financial updates beyond this range. We will share additional information when we announce our second-quarter financial results in early August.”

“Our primary focus remains on addressing the needs of our customers, not only in the Gulf, but throughout North America,” McKim concluded. “While this oil spill response requires us to marshal a substantial amount of resources, we anticipate no service disruptions to any of our ongoing client engagements in the Gulf region and throughout the U.S. and Canada. As we have proven through our emergency response work in the aftermath of Hurricane Katrina, and other oil spills in the Gulf region, we are able to draw significant leverage from our extensive network of assets and specialized equipment, and the recent addition of Eveready also affords us additional capacity.”

Clean Harbors has created a link – www.cleanharbors.com/gulfresponse – on its website to keep investors and interested stakeholders updated on the Company’s efforts. The site also contains links to other websites that provide spill-related information disseminated by the government and other agencies.

About Clean Harbors

North America’s Leading Environmental Emergency Response Provider

As North America’s premier environmental emergency response provider, Clean Harbors has been the leading responder to thousands of oil and chemical spills and natural disasters throughout the U.S., Canada and the Caribbean. The Company is uniquely prepared to undertake large scale responses without any disruption to its ongoing customer operations throughout North America. Over the past three decades, Clean Harbors played key roles for various government agencies by responding to disasters including the World Trade Center terrorist attacks, decontaminating facilities contaminated with anthrax, and providing logistical support and clean-up activities in the Gulf Region in the wake of Hurricanes Katrina and Rita. Clean Harbors has also been a lead responder to major oil spills along the Atlantic, Gulf and Pacific coasts, the Great Lakes, and the Mississippi River.

Environmental, Energy and Industrial Services

Clean Harbors is the leading provider of environmental, energy and industrial services, and hazardous waste management services throughout North America. The Company serves more than 50,000 customers, including a majority of the Fortune 500 companies, thousands of smaller private entities and numerous federal, state, provincial and local governmental agencies.

Headquartered in Norwell, Massachusetts, Clean Harbors has more than 175 locations, including over 50 waste management facilities, throughout North America in 36 U.S. states, seven Canadian provinces, Mexico and Puerto Rico. The Company also operates international locations in Bulgaria, China, Sweden, Singapore, Thailand and the United Kingdom. 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, and involve risks and uncertainties. These forward-looking statements are generally identifiable by use of the words “believes,” “expects,” “intends,” “anticipates,” “plans to,” “estimates,” “projects,” or similar expressions. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those reflected in these forward-looking statements. Such statements may include, but are not limited to, statements about the benefits of the acquisition of Eveready, including future financial and operating results, the combined company’s plans, objectives, expectations and intentions and other statements that are not historical facts. Such statements are based upon the current beliefs and expectations of Clean Harbors’ management and are subject to significant risks and uncertainties. Readers are cautioned not to place undue reliance on these forward-looking statements, which reflect management’s opinions only as of the date hereof. The Company undertakes no obligation to revise or publicly release the results of any revision to these forward-looking statements other than through its various filings with the Securities and Exchange Commission. A variety of factors may affect the Company’s performance, including, but not limited to:

• The uncertain nature of the duration and scope of the Company’s involvement in the Gulf of Mexico emergency environmental response effort;
• The Company’s ability to manage the significant environmental liabilities that it assumed in connection with prior acquisitions;
• The availability and costs of liability insurance and financial assurance required by governmental entities related to the Company’s facilities;
• General conditions in the oil and gas industries, particularly in the Alberta oil sands and other parts of Western Canada;
• The possibility that the expected synergies from the acquisition of Eveready will not be timely or fully realized;
• The extent to which the Company’s major customers commit to and schedule major projects;
• The Company’s future cash flow and earnings;
• The Company’s ability to meet its debt obligations;
• The Company’s ability to increase its market share;
• The effects of general economic conditions in the United States, Canada and other territories and countries where the Company does business;
• The effect of economic forces and competition in specific marketplaces where the Company competes;
• The possible impact of new regulations or laws pertaining to all activities of the Company’s operations;
• The outcome of litigation or threatened litigation or regulatory actions;
• The effect of commodity pricing on overall revenues and profitability;
• Possible fluctuations in quarterly or annual results or adverse impacts on the Company’s results caused by the adoption of new accounting standards or interpretations or regulatory rules and regulations;
• The effect of weather conditions or other aspects of the forces of nature on field or facility operations;
• The effects of industry trends in the environmental services, energy and industrial services marketplaces; and
• The effects of conditions in the financial services industry on the availability of capital and financing.

Any of the above factors and numerous others not listed nor foreseen may adversely impact the Company’s financial performance. Additional information on the potential factors that could affect the Company’s actual results of operations is included in its filings with the Securities and Exchange Commission, which may be viewed on www.cleanharbors.com/investor_relations.

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