How likely are you to get cancer from entering buildings in California?
And how would you know?
To the best of my memory, the first time I entered California, I was hesitant to enter the hotel because there was a sign near the entrance, stating something along the lines of “Entering this building exposes you to cancer-causing chemicals”. Yet, the longer I stayed in California, the more confusion I felt. Was there a building in this state that didn’t contain this statement? It seemed unlikely that California’s buildings were made with some special groups of carcinogens that weren’t being made elsewhere. Yet, how much truth was there to these warnings?
These warnings were part of businesses adhering to Prop 65, whose purpose is defined as:
“Proposition 65 requires businesses to provide warnings to Californians about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm. Exposure to these chemicals may take place when products are acquired or used. Exposure may also occur in homes, workplaces, or other environments in California. By requiring that this information be provided, Proposition 65 enables Californians to make informed decisions about their exposures to these chemicals.”
This is vague. What is significant exposure? What is there to make a decision about, if virtually every building exposes you to carcinogens? I’m not particularly inclined towards a nomadic life, frolicking in the woods. Let’s find out.
What is Significant Exposure, According to Prop 65?
For carcinogens:
The No Significant Risk Level (NSRL) is when, upon being exposed to the chemical for 70 years, you wouldn't have over a 1/100,000 chance of developing cancer because of the exposure.
For chemicals causing reproductive/birth defects:
The No Observable Effect Level (NOEL) is the highest level of the chemical that we have proven causes no harm. This number divided by 1,000 is the Maximum Allowable Dose Level (MADL). If there is exposure to a chemical higher than the MADL, a warning is required.
Determining these levels can be burdensome for businesses, so OEHHA has a list of 300 common chemicals and their acceptable levels of exposure.
Potassium Bromate
Interestingly, the NSRL for potassium bromate is 1 microgram per day. Tying back to an earlier post about additives allowed in our food, one study in Cameroon found that there was 48.50 mg/kg to 10148.50 mg/kg of potassium bromate in the bread. That is very concerning for the innocent Cameroon citizens, but not directly relevant to the question we are answering. They also pointed out that the recommended amount of maximum potassium bromate recommended by the FDA is 50 mg/kg - this translates to 50 000 micrograms/kg, which is far more than one microgram potassium bromate per slice of bread. I wonder why this discrepancy exists - between the 1 microgram and nearly 2000 micrograms of potassium bromate per slice of bread (with the assumption that about 26 slices of bread are in one kg). This is a massive discrepancy between the FDA and the OEHHA.
This is odd, but surely this is an exception, not the rule. Let’s take a look at some other chemicals.
Glyphosate
Glyphosate is a compound found in many places, including in tap water. The OEHHA’s safe harbour for glyphosate is 1100 micrograms per day. They have their reasoning behind this freely available in pdf form on the website here. Another interested party, the Environmental Working Group, had an interestingly lower number. They recommend 5 ppb for glyphosate for a one-in-a-million lifetime risk of cancer, which we can translate to 50 ppb for a 1/100,000 chance, and then using simple stoichiometry, translate into 470 micrograms of glyphosate for every liter of water you drink. Given that the average Californian drinks just below two liters of water a day, the OEHHA’s safe harbour of 1100 micrograms per day seems approximately accurate… without the consideration that we are exposed to glyphosate from other sources.
(Stoichiometry, if you wish to verify)
1 liter of water is about 55.55 moles of water, which corresponds to approximately 2.7775e-6 moles of glyphosate, and using its molar mass of 169.07 g/mol, is approximately 4.7e-4 g, or 4.7e2 micrograms per liter.
Asbestos
Asbestos is limited to 100 microfibers a day. This is hard to quantify in terms of impact, and I couldn’t find any alternative research papers which quantified this in terms of risk. (As a refresher, the OEHHA’s significant level is so that exposure to this level for 70 years only gives you a 1/100,000 chance of developing cancer). If we consider this in the context of the workplace, an EU organization quantified the US’s method as measuring this as 0.1 fibers/cm^3 over 8 hours (page 17). Yet, this also translates to 125 cases per 100,000 people exposed (page 9). This seems concerning. 125 >>>1.
Implications
If we assume even minimal levels of exposures to chemicals are harmful enough to warrant exposure warnings - all of which follow very similar, if not identical formats, this actually reduces the ability of the individual to make informed decisions. If something that has a 1/100,000 chance of causing us cancer if we’re exposed to it for 70 years is given the same amount of caution as something that has a 1/2 chance of causing cancer under the same conditions, we are not able to make any manner of an informed decision. I would enter a building under the first scenario, but not the second.
This is even discounting the miscalibrated risks the USA seems to have. Acceptable potassium bromate levels have a great discrepancy between the FDA and OEHHA. Glyphosate seems to be slightly under-evaluated in risk. Asbestos fibers are grossly underestimated in risk by over a hundred-fold, if the research done by the EU is credible.
Do better.