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November 10, 2022 5 min read

What is Proposition 65?

California’s Proposition 65 (Prop 65), also known as the Safe Drinking Water and Toxic Enforcement Act of 1986, was a ballot initiative voted into state law more than three decades ago.

It was created in reaction to the discovery of dangerous pollutants contaminating the California water supply.

It requires businesses to inform Californians about exposure to chemicals known to cause cancer, birth defects or other reproductive harm. By mandating that this information be provided, Prop 65 enables Californians to make educated decisions about their exposures to these chemicals.

Prop 65-listed chemicals represent a wide range of naturally occurring and synthetic chemicals that include additives or ingredients in pesticide formulations, common household products, food, drugs, dyes, or solvents [1].

When enacted, Prop 65 accomplished five things [2]:

  1. It creates a list of chemicals (including a number of agricultural chemicals) known to cause cancer or reproductive toxicity;
  2. It limits discharges of listed chemical to drinking water sources;
  3. It required prior warning before exposure to listed chemicals by anyone in the course of doing business
  4. It creates a list of chemicals requiring testing for carcinogenicity or reproductive toxicity; and
  5. It required the Governor to consult with qualified experts (a 12-member Scientific Advisory Panel as necessary to carry out his duties.

It now extends far beyond drinking water, though. “Businesses” means anyone who sells anything that may cause exposure, above “safe harbor” levels, to a long and growing list of chemicals that the state of California is required to update each year.

In 1988, when the warning requirements went into effect, the list included 235 chemicals.

Currently it has about 900 toxins and carcinogens on it. If a product that is sold in California includes one of those 900 chemicals, it requires the Prop 65 warning label.

Although federal agencies like the Food and Drug Administration and the Environmental Protection Agency already set levels for safe consumption of chemicals, Prop 65 goes above and beyond federal standards, sometimes setting different limits than the EPA does.

More information can potentially help, which is why Prop 65 was amended in 2016 to mandate that labels name at least one harmful chemical ingredient that triggered the warning. Consumers can look up fact sheets [3] about each chemical on the OEHHA website to learn about the risks associated with it.

Why are we seeing an increase in warning labels?

There are two big reasons why we are seeing so many warning labels on a law that is three decades old:

  1. E-commerce
  2. Lawsuits

As commerce moves increasingly online, California products are showing up everywhere now, and the warning labels along with them.

In August 2018, new OEHHA regulations took effect, requiring websites that sell products that qualify for the warning to include these labels. Therefore, you may have recently seen more warnings on e-commerce sites like Amazon.

As e-commerce business continues to grow and inventory travels across state lines, more companies are putting the labels on everything—even on items that are not necessarily bound for California—to avoid being sued.

Failure to comply can leave a company liable for fines of up to $2,500 per violation per day, according to OEHHA. The labeling onus is on brands and retailers, and court cases have risen as the list of chemicals keeps growing longer.

The problem with Prop 65

Prop 65 sets very low thresholds for warnings. For birth defects, warnings are required at one-thousandth of the level at which a certain chemical is shown to cause birth defects. For example, Acrylamide was added to the list in 1990 after studies linked it to cancer [4].

This chemical, which appears during the process of frying or roasting, has led to cancer warnings on everything from coffee to prune juice in California. The American Cancer Society states that there is no connection between acrylamide and cancer [5], the Food & Drug Administration  stated that is isn’t feasible or necessary to completely eliminate acrylamide from one’s diet [6].

A recent paper from Harvard Kennedy School argues that current government warning systems, including Prop 65, do a terrible job at distinguishing between large and small risks. When there is an overabundance of warnings about small harms, people become conditioned and tend to ignore them. This can be dangerous when real dangers arrive and no one is heeding the warnings anymore.

Prop 65 labels indicate that a toxic chemical is present in a given product, but they tell us nothing about how high the level of exposure is, and how relatively dangerous the chemical is, compared with others. Therefore, Proposition 65 warnings definitely do not pass the test of providing accurate or useful information to consumers [7].

Should you worry about Prop 65 warning?

The law has been heavily criticized for causing unnecessary worry and over-warning about cancer and reproductive risks. The Prop 65 label is like a noisy alarm that rings equally loudly about smaller amounts of low-risk substances and huge amounts of potentially harmful chemicals.

As stated, the labels do not say how much of the chemical is present, or how much it would really take to make a person sick. You could get the same alarming label on potato chips (acrylamide), chemotherapy (uracil mustard), or lumber (wood dust).

It’s obviously helpful to be alerted to the presence of potentially harmful chemicals, but not all doses of these different chemicals mean the same thing.

If you see a Prop 65 warning on a product you might eat or put on your skin, take a closer look at it.

Check the ingredients for anything that might be suspicious—beauty and personal care are a good example of this. If there is a label, then there are at least trace amounts of an ingredient that has been linked to cancer or reproductive harm. However, in many cases these ingredients are trace amounts.

Often, the risk of harm was found only in animal studies where massive amounts of the ingredient were given to the animal.

Be cautious and check ingredients, but don't overly worry about the Prop 65 label, which quite often can be needlessly alarming.

1.    Reddam, A. and D.C. Volz, Inhalation of two Prop 65-listed chemicals within vehicles may be associated with increased cancer risk. Environ Int, 2021. 149: p. 106402.
2.    Kilgore, W.W., California's Proposition 65: extrapolating animal toxicity to humans. Am J Ind Med, 1990. 18(4): p. 491-4.
3.    Welcome to the Proposition 65 Warnings Website. Available from:  
4.    Bull, R.J., et al., Carcinogenic effects of acrylamide in Sencar and A/J mice. Cancer Res, 1984. 44(1): p. 107-11.
5.     ; Available from:
6.    You Can Help Cut Acrylamide in Your Diet. Available from:
7.    Robinson, L.A.a.V., W. Kip and Zeckhauser, Richard J.,, Efficient Warnings, Not "Wolf or Puppy" Warnings, in HKS Working Paper No. RWP16-033. 2016: Harvard Kennedy School.

Dr. Paul Henning

About Dr. Paul

I'm currently an Army officer on active duty with over 15 years of experience and also run my own health and wellness business. The majority of my career in the military has focused on enhancing Warfighter health and performance. I am passionate about helping people enhance all aspects of their lives through health and wellness. Learn more about me