3 ms·

If the research in PFAS is at all like the article posted yesterday which did multiple statistical tests without doing the appropriate correction, I am not con

If the research in PFAS is at all like the article posted yesterday which did multiple statistical tests without doing the appropriate correction, I am not convinced that PFAS are all that harmful. Because PFAS are so widespread and they have been around so long, if they were really bad we would be seeing massive issues. However, we are not. Likely they do cause some harm if you have enough statistical power, but likely below the threshold that we live with (for example birth control, going to the beach, driving a car, red meat, and maybe even cooking itself).

7sidedmarble 4y ago
>Likely they do cause some harm if you have enough statistical power, but likely below the threshold that we live with (for example birth control, going to the beach, driving a car, red meat, and maybe even cooking itself). Isn't the entire reason these things are unsafe that they bioaccumulate over long periods of small dose exposure?
- landemva 4y ago
  I am interested in where/if this bioaccumulates, like mercury does in marine life.
defterGoose 4y ago
| and they have been around so long, if they were really bad we would be seeing massive issues. However, we are not. 1. They really haven't "been around so long". Not even a single human lifetime. 2. Plenty of other things cause cancer, endocrine disruption etc. Red meat and the beach are here to stay, but why should I be ok with some unaccountable corporation dumping additional pollutants into my environment? But, by all means, continue to avoid a rational, cautious mode of decision making. It's probably not that harmful in my opinion.
edgyquant 4y ago
Interesting thought, can you talk more about the methods and their flaws? Also what’s the article you’re referring to?
- RcouF1uZ4gsC 4y ago
  The discussion is https://news.ycombinator.com/item?id=32438368#32442794 https://news.ycombinator.com/item?id=32438368#32442794 Here is my comment: This is actually very poor statistics. Take a look at the actual study: https://www.jhep-reports.eu/article/S2589-5559(22)00122-7/fulltext https://www.jhep-reports.eu/article/S2589-5559(22)00122-7/fu... And look at table 3. They are testing 6 different types of PFAS, and only 1 is statistically significant. They need to be using the Bonferroni Correction because they are checking multiple hypothesis. To do that, you divide the required p-value (0.05) by the number of tests (6). If you do the Bonferroni Correction, none of the PFAS is statistically significant. Relevant XKCD: https://xkcd.com/882/ https://xkcd.com/882/ Thus the real conclusion is that the study did not find any statistically significant link between 'forever chemicals' and liver cancer.
  - mbreese 4y ago
    In the text they mention an FDR correction. In which case you typically don’t use 0.05 as the threshold. Bonferroni isn’t the only way to do that correction, but it a valid method (depending on the pvalue distribution). But with only 6 tests, it’s not really that critical. I usually only think of multiple testing correction in the context of thousands of tests. Given your comment I was expecting something like 5 patients per group. But they had 50 cases and 50 controls. In this context, an uncorrected pvalue of 0.02 is pretty solid.

7sidedmarble 4y ago

>Likely they do cause some harm if you have enough statistical power, but likely below the threshold that we live with (for example birth control, going to the beach, driving a car, red meat, and maybe even cooking itself). Isn't the entire reason these things are unsafe that they bioaccumulate over long periods of small dose exposure?

landemva 4y ago
I am interested in where/if this bioaccumulates, like mercury does in marine life.

defterGoose 4y ago

| and they have been around so long, if they were really bad we would be seeing massive issues. However, we are not. 1. They really haven't "been around so long". Not even a single human lifetime. 2. Plenty of other things cause cancer, endocrine disruption etc. Red meat and the beach are here to stay, but why should I be ok with some unaccountable corporation dumping additional pollutants into my environment? But, by all means, continue to avoid a rational, cautious mode of decision making. It's probably not that harmful in my opinion.

edgyquant 4y ago

Interesting thought, can you talk more about the methods and their flaws? Also what’s the article you’re referring to?

RcouF1uZ4gsC 4y ago
The discussion is https://news.ycombinator.com/item?id=32438368#32442794 https://news.ycombinator.com/item?id=32438368#32442794 Here is my comment: This is actually very poor statistics. Take a look at the actual study: https://www.jhep-reports.eu/article/S2589-5559(22)00122-7/fulltext https://www.jhep-reports.eu/article/S2589-5559(22)00122-7/fu... And look at table 3. They are testing 6 different types of PFAS, and only 1 is statistically significant. They need to be using the Bonferroni Correction because they are checking multiple hypothesis. To do that, you divide the required p-value (0.05) by the number of tests (6). If you do the Bonferroni Correction, none of the PFAS is statistically significant. Relevant XKCD: https://xkcd.com/882/ https://xkcd.com/882/ Thus the real conclusion is that the study did not find any statistically significant link between 'forever chemicals' and liver cancer.
- mbreese 4y ago
  In the text they mention an FDR correction. In which case you typically don’t use 0.05 as the threshold. Bonferroni isn’t the only way to do that correction, but it a valid method (depending on the pvalue distribution). But with only 6 tests, it’s not really that critical. I usually only think of multiple testing correction in the context of thousands of tests. Given your comment I was expecting something like 5 patients per group. But they had 50 cases and 50 controls. In this context, an uncorrected pvalue of 0.02 is pretty solid.