Every star is anchored to a published study, regulatory document, or analytical method.
If a claim isn't traceable to a published study, a regulatory document (EPA, FDA, EFSA, NSF), or a standardized analytical method, it doesn't appear in our ratings. We will say 'evidence is mixed' before we will say something we can't cite. We will hedge before we will overstate. We have no editorial reason to invent science we can't find.
Pages of peer-reviewed journals — the source material that anchors every Hydrology University claim.
Most consumer-facing 'guides' to drinkware safety are written by brands selling drinkware. The conflict of interest is structural and unresolvable. Hydrology University accepts no manufacturer sponsorship for material ratings, no affiliate kickbacks, and no free product placements on these pages. That allows us to cite Mason 2018 and Qian 2024 on microplastics; Le 2008 on BPA migration; Olsson & Landolt 2003 on stainless passive layers; vom Saal 2005 on endocrine disruption — and to accurately note where evidence is still evolving.
Every quantitative claim links to a peer-reviewed primary source.
We weight regulatory and meta-analytic sources (EPA, FDA, NSF, EFSA, Cochrane reviews) heavily.
We acknowledge mixed or evolving evidence (e.g., long-term BPS exposure, dietary aluminum) explicitly rather than picking a side.
We update ratings when new high-quality evidence emerges.
Before publication in a reputable scientific journal, a study is reviewed by independent experts in the same field. They check methodology, statistics, the validity of the conclusions, and whether the data actually supports the claims. Peer review is far from perfect — it doesn't catch every flaw — but it is a meaningful filter. A peer-reviewed paper is an order of magnitude more reliable than a press release, blog post, or marketing claim.
We weight: study design (RCT > prospective cohort > cross-sectional > in vitro), sample size, replication by independent groups, conflicts of interest disclosed, and consistency with mechanism. A single small in-vitro study saying 'BPA is dangerous' becomes much more credible when echoed by twenty other studies, validated in animal models, and supported by epidemiology.
Long-term human health effects of BPS and BPF (BPA replacements) are still being characterized. The dietary contribution of aluminum to neurodegeneration remains debated. The total in-vivo health impact of microplastics is an active research front. We say 'evidence is mixed' or 'still evolving' on these topics — not to hedge, but because that's the actual state of the science.
Every material's research page lists named studies and citations under 'Background Research & Citations.' Click any material to inspect the source list.
Qian et al., PNAS (2024)
240,000 plastic particles per liter on average in popular bottled water brands using laser hyperspectral imaging.
Rochester & Bolden, Environ. Health Perspect. (2015)
Systematic review of 32 studies: BPS and BPF show estrogenic and antiandrogenic activity comparable to BPA.
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