Environmental Question #18 [Plasticizers in Milk]
I was checking out plasticlist.org and noticed milk bottled in glass had higher counts of some of the chemicals of milk bottled in plastic (such as the Straus Organic Milk in glass), and I was confused why this was...can you explain like I'm 5 to me?
Courtesy of Reddit user u/AngryBPDGirlQ: I was checking out plasticlist.org and noticed milk bottled in glass had higher counts of some of the chemicals of milk bottled in plastic (such as the Straus Organic Milk in glass), and I was confused why this was...can you explain like I'm 5 to me?
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A: First of all, thank you for introducing me to this website! I had never heard of it before, but it rocks and I'm very glad to know about it now.
All of the chemicals listed on this website are called "plasticizers." In scientific terms the word "plastic" just means "flexible," so a plasticizer is a chemical that is mixed into various materials to make them more flexible. As an example, water acts as a plasticizer in wood, and I'm sure you're already familiar with that. Dry wood is much less flexible than wet wood.
As I'm sure you're also aware, there are many different kinds of plastic, some hard and stiff, some soft and flexible. The type of plastic that is used for milk jugs is already inherently flexible, so little to no plasticizers are used to make milk jugs since they aren't necessary. Plasticizers are generally used to make tough, durable plastics more flexible, like for example bottle caps and the tubes in milking machines.
That is to say that the chemicals in this list most likely aren't getting into the milk through the bottles, they're probably coming from some other plastic equipment somewhere else in the process. Depending on what a given dairy farm's equipment is made of and how old their equipment is, different amounts of various chemicals will be leached out into the milk.
I want to put in perspective though, that all of the numbers listed for the milk on this website are EXTREMELY LOW. As an example, this website lists the chemical DIDP along with the EU daily exposure limit for it. The EU is generally very good and strict about chemical exposure, so I think this is a good example. The limit listed here is 150,000 nanograms per kilogram of body weight per day. I weigh about 80kg and this Straus milk has 66,480ng of chemicals per cup of milk. This means that for me to suffer negative health effects from chemical exposure through drinking this milk I would need to drink 180 cups of milk per day or about 11 gallons per day. I've never done the gallon challenge, but it looks like no fun, and if I were to drink 11 gallons of milk per day I would have a lot more pressing problems than chemical exposure.
Hello!
ReplyDeleteDo the limits matter if the plasticisers are thought to have non-monotonic dose responses? I.e. large effects at smaller doses and no / different effects at larger doses? My understanding is that any substance expected to be an endocrine disruptor has this problem, because it is only this much you need of the substance to drive cell level signalling (no more effect once all cell receptors doing the signalling have been bound with one molecule of the substance).
I appreciate that plasticlist.org are being quite prudent and don't want to scare people, basing their comments (as yourself) on regulatory limits.
But regulatory toxicity limits *assume* all substances have monitonic dose responses. That has been challenged by endocrinologists for a long time.
To the point that now, there are discussions on going in the EU around how to modify testing protocols to take this into account (https://www.efsa.europa.eu/en/efsajournal/pub/6877)
Given these new developments, is it far to lull people into a false sense of security by refering to existing toxicity limits?
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DeleteI'm glad you've been enjoying my work! Thank you for providing your source as well.
The nature of science is that practically every finding is being challenged constantly, so when communicating with the public I prioritize communicating only information that has been rigorously proven by scientific consensus to avoid confusing people unnecessarily. As an example of why a finding being challenged is not sufficient reason to publicize it, the Flat Earth community is very active in scientific publication. They don’t publish in broadly recognized journals, but Flat Earthers do conduct real experiments, attend conferences, and publish their results. If the existence of the globe is still being challenged despite the mountain of evidence and broad consensus, then a finding being challenged is not a good enough reason to alert the general public or raise any alarms.
That said, the challenges you’re raising are reasonable and credible, unlike assertions that the Earth is flat. However, scientists and doctors have not determined what threat the potential non-monotonic behavior of endocrine disruptors poses, if any. Here are a couple of quotes from the Conclusions section of the paper you linked from the European Food Safety Authority (which is a very credible source, thank you for providing it):
“Overall, it was concluded that:
There is currently no gold standard for the statistical assessment of NMDR for chemical risk assessment. Therefore, using different statistical approaches may result in diverging conclusions when used individually.”
“Evidence for non-monotonicity of apical effects should be assessed in terms of statistical rigor and biological plausibility. Indications of possible NMDR should be investigated and considered during the risk assessment process according to the process detailed in this Opinion.”
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The scientists here conclude that we currently lack effective statistical models for assessing the potential non-monotonicity of these chemicals, and further research must be conducted to determine what effect these chemicals have on the body. I’m not cherry-picking these quotes either, beyond choosing quotes that are somewhat more readable for general audiences. The entire conclusion section of the publication essentially boils down to, “We are suspicious of these chemicals, but we don’t have appropriate tools or data today to confirm or deny those suspicions, so more research must be conducted.” I completely agree with that conclusion. There is good reason to be suspicious, and more research in this area is absolutely needed.
Part (2/2)
DeleteResearch is already being conducted into the potential effects of endocrine disrupting compounds all over the world, but the data isn’t in yet, nor is appropriate context. Remember, that synthetic chemicals aren’t the only endocrine disruptors in the world, there are lots of natural endocrine disruptors too. Soybeans contain some naturally occurring endocrine disruptors, and many naturally occurring hormones in meat (even from animals who have no artificial hormones given to them) can act as endocrine disruptors. Many of these natural endocrine disruptors have also been shown to behave non-monotonically.
This is why further research and better models are necessary. To illustrate this point, I’ll make up a unit called the “Endocrine Disruption Unit” or EDU, and my imaginary unit adjusts for non-monotonic behavior to allow for direct comparison between monotonic and non-monotonic compounds using the same unit. (This kind of self-adjusting unit is very common in many fields, that’s why most greenhouse gases are measured in “equivalent CO2”) Today we know that many plastics and industrial chemicals contain >0 EDU. We also know that soybeans and meat have >0 EDU. However, we are not able to tell what the actual numbers are beyond knowing the numbers are greater than zero, because the tools we need to find that out are still being developed. In 10 years when we have the appropriate tools, we might find out that a plastic water bottle contains 1000 EDU, and a bowl of soybeans contains 10 EDU, then decide to ban plastic water bottles based on that. However, it is equally possible that we will find out that the plastic water bottle only contains 2 EDU and soybeans contain 8 EDU. In that case then we would need to decide whether to ban soybeans and/or accept the minor health risk of the plastic bottle.
Of course my goal is not to lull people into a false sense of security, my goal is to educate people on scientific information that has been rigorously proven, while minimizing the amount people worry about the unknown. I don’t know if endocrine disrupting chemicals are worth worrying about, and today no one in the world knows for sure either. I also don’t know if I’ll be hit by a car and die tomorrow, and no one in the world knows that either. How we manage that uncertainty is a decision that each of us needs to make for ourselves, and in my opinion the very real health harm caused by constant stress over the unknown is worth considering when deciding whether or not to share information that has not yet been fully vetted.
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I hope this answered your question! As you probably know, this is a very hard time to be a scientist in the US, particularly a scientist focused on safety and sustainability, so I am currently looking for work and doing what I can to make ends meet. If you found this helpful, I’d appreciate if you used the Paypal button above to send me a few bucks.