Every metal file at the hardware store bears a California Prop. 65 warning on the label. What could possibly be the cancer-causing agent in a solid metal file?


5 Answers 5


Some metal products may contain elements or chemicals known to the State of California to cause cancer, birth defects or reproductive harm. Like nickel, molybdenum, lead, chrome, etc. I would imagine that the file manufacturer labels the product out of an abundance of caution so they never have to worry about being sued or prosecuted, even if the materials in question are not normally present in harmful quantities.

  • 2
    I suspect you are right it is just CYA. Especially since many tools are produced by contract suppliers. The cost of verifying that none of the listed products were used is probably much harder than posting a Socialist Republic of California Prop 65 warning Commented Nov 22, 2019 at 17:20
  • 1
    @NoSparksPlease Before you post a Prop 65 warning on your product, you have to create a Safety Data Sheet regarding your product that details the specific danger posed by your product. It's not as simple as just slapping on a label. Commented Nov 25, 2019 at 12:41
  • I have a torque wrench with one of these labels on it. I have no idea what precautions I should take when attaching my lawnmower blade to avoid the danger. These labels are basically useless because so many things have them. They were even required on coffee for a brief period of time.
    – JimmyJames
    Commented Nov 25, 2019 at 14:34
  • Yup, stay focused on the important safeguards; for you- disconnect (maybe even remove) the mower's spark plug! Commented Nov 27, 2019 at 1:42


If using the product can release the chemical then slap a sticker on it.

I think it's just an overzealous interpretation of:

Proposition 65 requires businesses to provide warnings to Californians about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm. These chemicals can be in the products that Californians purchase, in their homes or workplaces, or that are released into the environment. By requiring that this information be provided, Proposition 65 enables Californians to make informed decisions about their exposures to these chemicals.




Depending on the alloy, tool steel probably contains cobalt and/or nickel. These are listed on Prop 65.


  • Cobalt metal powder
  • Cobalt oxide


  • Nickel (Metallic)
  • Nickel compounds (due to the ambiguity in this line, anything with nickel)
  • Nickel oxide

Additionally, there are other metal compounds of chromium, vanadium and even iron that are listed, but I doubt these items molecules could actually be found in tool steel.

  • I doubt it contains Ni. It should contain Cr. Nickel makes steel workable, weldable and more oxidation resistant. Cr makes it harder and oxidation resistant and promotes the austenite->martensite transformation. But it is likely not an alloy steel, unless it is a special purpose branded file, so going to be less than 4-5% of whatever - and the whatever is most likely dominated by Cr.
    – Stian
    Commented Nov 22, 2019 at 17:27
  • 1
    @StianYttervik Sorry, but I work in the metals industry. ALL of the air hardened and all of the shock-resistant tool steel alloys have nickel in them. Yes, the steel used to make files (specifically) will probably have more chromium in it, but chromium is on Prop 65 only as hexavalent compounds, which would only be formed if you were welding your file or heating it to some extreme temperature. This is why I didn't include it in the list. Commented Nov 25, 2019 at 12:38

Because of the things you'll be filing with it

The same reason sandpaper and other paint-prep supplies contain warnings of lead. The sandpaper doesn't contain lead; but good chance what you're sanding does.

To be more specific, you're referring to the text of a Prop 65 warning, presumably text out of 27 CCR 25603(a) affixed to the product package per 25602(a)(3). The manufacturer is using this language because it's defined as a Safe Harbor, as per 26501 and onward. A "Safe Harbor" is a "Get out of Jail Free" card for litigation. (the wisdom of this is debatable, but that's neither here nor there).

The labeling is called for here:

27 CCR 25600.2. Responsibility to Provide Consumer Product Exposure Warnings.

(b) The manufacturer, producer, packager, importer, supplier, or distributor of a product may comply with this article either by affixing a label to the product bearing a warning ...

A pivotal question raised in heated commentary (now deleted) is whether this applies to the product itself or to the foreseeable uses of the product.

enter image description here src

This red cage is just steel. It can't explode. Why does it need a warning label?

Let's look at 25600.1 Definitions, defining the terms of art used in the regulation.

(d) “Consumer product” means any article, or component part thereof, including food, that is produced, distributed, or sold for the personal use, consumption or enjoyment of a consumer.

(e) “Consumer product exposure” means an exposure that results from a person’s acquisition, purchase, storage, consumption, or any reasonably foreseeable use of a consumer product, including consumption of a food.

Italics mine; note this is the difference that decides the question.

Well, then, it's pretty clear what 25600.2 is talking about then. Right?

25600.2. Responsibility to Provide Consumer Product Exposure Warnings
25600.2. Responsibility to Provide Consumer Product Exposure Warnings

I personally don't have any trouble seeing the the second one as correct; it specifically invokes a defined term-of-art, and otherwise "exposure" would modify "warnings" and that doesn't make much sense. But I'll concede that's uncertain and this might be an Oxford Comma kind of a deal. So how do we settle that?

Easy. Safe Harbor protection is optional for the manufacturer. Speak the magic incantation; get a liability shield. Or don't and takes yer chances. It rather defeats the purpose to unnecessarily make yourself a legal test case on the Oxford Comma, so to speak.

So yeah. It's about what you'll foreseeably be filing.


Work with metals can release ions or vapors of carcinogens, and other substances found in the vicinity might be the same. Here's a list of some common ones. In particular, wood dust, asbestos, arsenic, and chromium are particularly common in certain construction materials one might use a file or rasp on.

Hexavalent chromium is particularly a nasty chemical and when you file some steel that his been plated with chrome, you're raising the odds of being exposed to it. Iron workers, masons, carpenters, painters, and welders all have increased risks of various cancers because of sustained occupational exposure to particulate.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.