Is the California court ruling that coffee can increase cancer risk justified?
<p>A court in California <a href="https://www.cnn.com/2018/03/30/health/coffee-cancer-court-decision-warning-label-california/index.html" rel="nofollow noreferrer">ruled against companies that may have to put a warning that tells customers there is a possible cancer risk linked to coffee</a> by saying the companies "failed to meet their burden of proof on their Alternative Significant Risk Level affirmative defense". Is this ruling justified?</p>

<p>This is somewhat related to <a href="https://skeptics.stackexchange.com/a/36852/44006">this answer</a> since it addresses the health risk of acrylamide which is the court's argument for why coffee should have the cancer risk warning. Given the convincing data in the answer I linked, I'm finding it hard to see how the court justified this ruling.</p>

<p>From a legal perspective, I think the ruling is <em>reductio ad absurdum</em> correct. California voters passed Proposition 65. Consequently, <a href="https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC&amp;sectionNum=25249.6." rel="nofollow noreferrer">CA Health and Safety Code 25249.6</a> says "No person in the course of doing business shall knowingly and intentionally expose any individual to a chemical known to the state to cause cancer or reproductive toxicity without first giving clear and reasonable warning to such individual, except as provided in <a href="https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC&amp;sectionNum=25249.10" rel="nofollow noreferrer">Section 25249.10</a>". <a href="https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC&amp;sectionNum=25249.8" rel="nofollow noreferrer">Section 25249.8</a> mandates a list, and defines "known to the state"</p>

<blockquote>
  <p>A chemical is known to the state to cause cancer or reproductive
  toxicity within the meaning of this chapter if in the opinion of the
  state’s qualified experts it has been clearly shown through
  scientifically valid testing according to generally accepted
  principles to cause cancer or reproductive toxicity, or if a body
  considered to be authoritative by such experts has formally identified
  it as causing cancer or reproductive toxicity, or if an agency of the
  state or federal government has formally required it to be labeled or
  identified as causing cancer or reproductive toxicity.</p>
</blockquote>

<p>Acrylamide is <a href="https://oehha.ca.gov/proposition-65/chemicals/acrylamide" rel="nofollow noreferrer">so listed</a>, and has been for 18 years, reason code listed as "AB-IARC, AB-US EPA". The law does not say that "the benefits may outweigh the risks", nor does the law say anything about usual doses. There is an "escape clause", if one (the defendant) can prove that there is no effect (25249.8(b)):</p>

<blockquote>
  <p>An exposure for which the person responsible can show that the
  exposure poses no significant risk assuming lifetime exposure at the
  level in question for substances known to the state to cause cancer,
  and that the exposure will have no observable effect assuming exposure
  at one thousand (1000) times the level in question for substances
  known to the state to cause reproductive toxicity, based on evidence
  and standards of comparable scientific validity to the evidence and
  standards which form the scientific basis for the listing of such
  chemical pursuant to subdivision (a) of Section 25249.8. In any action
  brought to enforce Section 25249.6, the burden of showing that an
  exposure meets the criteria of this subdivision shall be on the
  defendant.</p>
</blockquote>

<p>The answer on Skeptics does not address <a href="https://www.epa.gov/sites/production/files/2016-09/documents/acrylamide.pdf" rel="nofollow noreferrer">the EPA finding</a> (and the science underlying it). At this point we can only conjecture about the defense's scientific argument (the ruling is still in the works, pending feedback from parties), but the judge said "While plaintiff offered evidence that consumption of coffee increases the risk of harm to the fetus, to infants, to children and to adults, defendants' medical and epidemiology experts testified that they had no opinion on causation" and that the coffee makers hadn't presented the proper grounds at trial to prevail. </p>

<p>Insofar as human subjects testing of suspected carcinogens is illegal, any argument that "but this only shows that it causes cancer in rats" is legally empty: rats are a suitable proxy for humans. <a href="https://oehha.ca.gov/media/downloads/proposition-65/chemicals/1007114meifindings.pdf" rel="nofollow noreferrer">This</a> is a state report addressing a potential carcinogen, 4-Methylimidazole. The report notes that to have a No Significant Risk Level finding, the substance must have less than a "daily intake level posing a 10^-5 lifetime risk of cancer". A further requirement is that "risk analysis shall be based on the most sensitive study 
deemed to be of sufficient quality" (whatever that is). This study mentions a previous study which was rejected because "these studies do not meet the criteria specified in Section 25703(a) because the experiments were not designed to adequately control for and examine the potential carcinogenicity of 4-MEI". Basically, Spiegelhalter's argument is too meta, and doesn't constitute a proof that acrylamide poses no risk of cancer.</p>

<p>If the defendants commissioned an independent scientific study to overcome earlier carcinogen findings, perhaps the study failed on technical grounds. The bar that has to be cleared is very high. The <a href="https://safewater.zendesk.com/hc/en-us/articles/211403878-4-What-are-EPA-s-drinking-water-regulations-for-acrylamide-" rel="nofollow noreferrer">EPA regulation</a> says that the maximum contaminant level goal for acrylamide is zero. That is the carcinogen-science basis for specific allowable levels in water supplies.</p>

<blockquote>
  <p>A court in California ruled against companies that may have to put a
  warning that tells customers there is a possible cancer risk linked to
  coffee by saying the companies "failed to meet their burden of proof
  on their Alternative Significant Risk Level affirmative defense". Is
  this ruling justified?</p>
</blockquote>

<p>Without seeing all of the evidence and legal arguments made, there is no way to know. It comes down to the weight of the evidence in the eye of the judge.</p>

<p>The burden of proof for an affirmative defense generally is upon the party to the lawsuit that raises that affirmative defense. But, whether the evidence was or was not sufficient to meet that burden of proof is impossible to know without sitting through a hearing and reviewing all of the evidence presented on that issue.</p>

<p>Usually, appellate courts will defer to a trial judge on the question of whether a burden of proof was met unless "no reasonable judge" could have come to that conclusion based upon the evidence presented.</p>

california civil-procedure health safety