Which is safer for my health: glass or stainless steel?

From a pure toxicology and materials science standpoint, borosilicate glass and food-grade 18/8 stainless steel are both completely inert materials that won't react with your beverages or release any harmful substances. Glass is essentially melted sand (silicon dioxide) that's chemically stable, while quality stainless steel creates a passive chromium oxide layer that prevents any metal ions from entering your water. Neither material contains BPA, phthalates, or other endocrine disruptors found in plastics. The safety difference comes down to physical safety: glass can shatter into sharp fragments that pose injury risks, particularly concerning for children or active use. Stainless steel is virtually indestructible. So while both are equally safe from a chemical exposure perspective, stainless steel adds physical safety that glass cannot match.