Document ID: ./input/supremecourt_opinions/opinions/06pdf/05-1120.pdf
Page Number: 32.0

26 

MASSACHUSETTS v. EPA 

Opinion of the Court 

Because  EPA  believes  that  Congress  did  not  intend  it  to 
regulate substances that contribute to climate change, the
agency maintains that carbon dioxide is not an “air pollut-
ant” within the meaning of the provision. 

The statutory text forecloses EPA’s reading.  The Clean 
Air  Act’s  sweeping  definition  of  “air  pollutant”  includes 
“any  air  pollution  agent  or  combination  of  such  agents, 
including  any  physical,  chemical  . . .  substance  or  matter 
which  is  emitted  into  or  otherwise  enters  the  ambient 
air . . . .”    §7602(g)  (emphasis  added).  On  its  face,  the 
definition  embraces  all  airborne  compounds  of  whatever
stripe,  and  underscores  that  intent  through  the  repeated 
use of the word “any.”25  Carbon dioxide, methane, nitrous 
oxide, and hydrofluorocarbons are without a doubt “physi-
cal  [and]  chemical  . . .  substance[s]  which  [are]  emitted
into . . . the ambient air.”  The statute is unambiguous.26 

Rather  than  relying  on  statutory  text,  EPA  invokes 

—————— 

25 See  Department  of  Housing  and  Urban  Development  v.  Rucker,  535 
U. S. 125,  131 (2002) (observing that “ ‘any’ . . . has  an  expansive  mean-
ing, that is, one or some indiscriminately of whatever kind” (some inter-
nal quotation marks omitted)). 

26 In  dissent,  JUSTICE  SCALIA  maintains  that  because  greenhouse 
gases permeate the world’s atmosphere rather than a limited area near
the  earth’s  surface,  EPA’s  exclusion  of  greenhouse  gases  from  the 
category of air pollution “agent[s]” is entitled to deference under Chev-
ron  U. S. A.  Inc.  v.  Natural  Resources  Defense  Council,  Inc.  467  U. S. 
837  (1984).    See  post,  at  11–13.    EPA’s  distinction,  however,  finds  no 
support in the text of the statute, which uses the phrase “the ambient 
air” without distinguishing between atmospheric layers.  Moreover, it is 
a  plainly  unreasonable  reading  of  a  sweeping  statutory  provision 
designed  to  capture  “any  physical,  chemical  . . .  substance  or  matter
which is emitted into or otherwise enters the ambient air.”  42 U. S. C. 
§7602(g).  JUSTICE SCALIA does not (and cannot) explain why Congress
would  define  “air  pollutant”  so  carefully  and  so  broadly,  yet  confer  on
EPA  the  authority  to  narrow  that  definition  whenever  expedient  by
asserting that a particular substance is not an “agent.”  At any rate, no
party  to  this  dispute  contests  that  greenhouse  gases  both  “ente[r]  the 
ambient  air”  and  tend  to  warm  the  atmosphere.    They  are  therefore 
unquestionably “agent[s]” of air pollution.