I can see this paper being reported in yet another 'pesticides cause scary disease X' type way, but to my mind, the evidence in this paper is quite weak for several reasons. 

Firstly, the authors don’t actually say that pesticides cause prostate cancer, just that they found 22 pesticides that were statistically associated with prostate cancer and that more research is needed. An association between two things does not mean one caused the other; it is just an observation. The work is based on statistics, not direct experiments and the data on pesticide usage and exposure were estimated, not actually measured.

If we changed the variable under study from pesticide to almost anything else, such as age, sleep, lack of exercise, etc. and ran the same tests using the health records used here for pesticides, we would likely find more associations, but it would not mean there was a connection, just an association. More work would be needed to prove any hypothesis. No such work has been done in this study. The authors also don’t propose any mechanism by which any of the multiple herbicides identified might cause such an effect. We also need to keep in mind that our ability to detect cancer has also increased over the years, so more cases may not be because the disease prevalence is increasing, just that we are better at spotting it.

Secondly, none of the authors of this paper appear to be toxicologists or chemists. The paper talks about pesticides, but this is a catch-all term for anything used to kill pests—itself a broad term that can include things like insects, rodents, fungi, or plants. The chemicals listed are actually herbicides—e.g., they are designed to affect plants, not humans, and they are often quite different from each other both in chemical structure and biological effect. 

The other thing to remember is the adage that the dose makes the poison, everything is a posting if you have enough of it, including water. If we are saying something is toxic we need to also talk about what amount and what duration of exposure is needed to have this effect. Plenty of people use herbicides and don’t get prostate cancer.

So, while the work raises interesting research questions, I do not think the evidence or harm is strong if herbicides are used as directed.  The biggest risk factors for prostate cancer are age and genetics, neither of which we can control.

New research published in Cancer has identified 19 additional pesticides potentially linked to an increased risk of prostate cancer, including the widely used pesticide glyphosate. This expands on previous studies that associated pesticides including 2,4‐D, linuron, and carbaryl with prostate cancer.

Stanford University researchers employed an Environment-Wide Association Study (EWAS) design, analysing the use of 295 pesticides from farm surveys in over 3,000 US counties. These data were compared to prostate cancer rates in the same counties 10-18 years later, accounting for the slow-growing nature of prostate tumours. Four of the 22 pesticides were also associated with deaths from prostate cancer.

However, the study has limitations: it uses county-level data, which may not directly apply to individual exposures, and can only demonstrate associations rather than causation. Despite these limitations, the findings could have significant implications for public health policies and agricultural practices. The study underscores the need for further research into the potential long-term health effects of pesticide exposure, particularly in relation to prostate cancer risk.