<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CLEAN
HARBORS, INC. FORM 10-Q DATED SEPTEMBER 30, 2000 AS FILED WITH THE SECURITIES
AND EXCHANGE COMMISSION AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 9-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> SEP-30-2000
<CASH> 1,118
<SECURITIES> 504
<RECEIVABLES> 51,831
<ALLOWANCES> 1,368
<INVENTORY> 2,860
<CURRENT-ASSETS> 56,921
<PP&E> 143,243
<DEPRECIATION> 87,121
<TOTAL-ASSETS> 149,165
<CURRENT-LIABILITIES> 92,456
<BONDS> 16,808
0
1
<COMMON> 111
<OTHER-SE> 38,459
<TOTAL-LIABILITY-AND-EQUITY> 149,165
<SALES> 0
<TOTAL-REVENUES> 175,269
<CGS> 0
<TOTAL-COSTS> 124,289
<OTHER-EXPENSES> 39,069
<LOSS-PROVISION> 513
<INTEREST-EXPENSE> 6,998
<INCOME-PRETAX> 4,400
<INCOME-TAX> 294
<INCOME-CONTINUING> 4,106
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 4,106
<EPS-BASIC> 0.34
<EPS-DILUTED> 0.33
</TABLE>