Soon California will monitor #microplastics in #drinkingWater and inform consumers. Law requires @CaWaterBoards evaluate #humanHealth risks and consider developing a numerical guidance level.

We convened an expert workshop to inform the state.
🧵(1/10)
microplastics.springeropen.com/articles/10.11…
We started by scraping the literature for toxicity studies. Of the >220 studies, 74 were relevant for humans. We focused on in vivo studies (n = 41) due to the lack of a framework for quantitative assessing in vitro particle toxicity data.

(2/10)
@todd_gouin et al. screened each study for relevance and reliability for understanding impacts. No single study met all criteria, so a subset was selected as being absolutely critical for evaluation (red criteria).
Most studies did not use enough doses to pass criteria.

(3/10)
12 studies passed the first screening tier, which we then evaluated with the help of 7 external experts in each study's field. Each study and endpoint was evaluated individually.

(4/10)
Experts agreed that there was insufficient evidence was available to derive a regulatory level level, but that we should derive a non-regulatory screening level to inform monitoring.

(5/10)
7 studies reported impacts on male rodents, with 4 considered reliable by experts.

We estimated thresholds for reliable endpoints using benchmark dose modelling.

Notably, effect thresholds were fairly consistent across studies and particle sizes for polystyrene spheres.
(6/10)
Using the most sensitive endpoint (AMH reduction in females), the most conservative screening level for drinking water is 91 particles/L, which is aligned to 1 to 5,000 um particles based on mass as the toxicologically relevant metric.

(7/10)
⚠️That conservative threshold comes with *extremely* high uncertainty - mostly driven by a lack of data for drinking water's relative source contribution and not understanding which particle trait drives toxicity (e.g., mass, surface area, volume, etc.).

(8/10)
While we have reliable indications of adverse impacts of polystyrene particles to male reproductive function in rodents, we need more information to quantitatively relate to humans.

@DrLeahTH et al. describe research needed to evaluate risks.

(9/10)
microplastics.springeropen.com/articles/10.11…
As more toxicity studies are published, they may be uploaded to the open database in @ToMExApp to allow more rapid meta-analyses.

We also made interactive data viz for this study in the app!
microplastics.springeropen.com/articles/10.11…

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Scott Coffin, Ph.D.

Scott Coffin, Ph.D. Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Don't want to be a Premium member but still want to support us?

Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal

Or Donate anonymously using crypto!

Ethereum

0xfe58350B80634f60Fa6Dc149a72b4DFbc17D341E copy

Bitcoin

3ATGMxNzCUFzxpMCHL5sWSt4DVtS8UqXpi copy

Thank you for your support!

Follow Us on Twitter!

:(