Clean Harbors, Inc. (“Clean Harbors”) (NYSE: CLH) announced today that it has commenced a follow-on public offering of 6.0 million shares of its common stock. The underwriters for the offering will also have the option to purchase up to an additional 900,000 shares of common stock. Clean Harbors intends to use the net proceeds of the offering to finance a portion of the purchase price for its previously announced proposed acquisition of Safety-Kleen, Inc. and its subsidiaries and related transaction fees and expenses. Goldman, Sachs & Co. is acting as the sole book-running manager of the offering. BofA Merrill Lynch and Credit Suisse Securities (USA) LLC are acting as co-managers. The shares are being offered only pursuant to the preliminary prospectus supplement to the base prospectus included in a registration statement, which was filed with the Securities and Exchange Commission and became effective on November 26, 2012. Copies of the preliminary prospectus supplement (and base prospectus) may be obtained by visiting the SEC's website at www.sec.gov or by contacting Goldman, Sachs & Co., Attn: Prospectus Department, 200 West Street, New York, NY 10282, telephone (866) 471-2526 or email at email@example.com. This release shall not constitute an offer to sell or the solicitation of an offer to buy any of these securities, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state. 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 Clean Harbors’ proposed acquisition of Safety-Kleen and business outlook and financial guidance and other statements that are not historical facts. Such statements are based upon the beliefs and expectations of Clean Harbors’ 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 various filings with the Securities and Exchange Commission, which may be viewed in the “Investors” section of Clean Harbors’ website.