Polyphosphates interact strongly with iron, aluminum, manganese, calcium, and lead, and the positive effect of polyphosphate complexation on lead solubility is particularly important from a public health perspective. In a different water system-with different water quality-we reported evidence of lead-polyphosphate complexation using the SEC-ICP-MS method summarized above. And while we did not identify similar complexes in samples from more than 20 homes in the system studied here, polyphosphate may have influenced lead release in ways that were not apparent from the data. For instance, polyphosphate might have dispersed colloidal iron or aluminum oxides that were also rich in lead, which is consistent with the SEC-ICP-MS data we report in the previous section (see Colloidal aluminum and lead in the distribution system). Furthermore, since polyphosphates revert to orthophosphate faster at higher temperatures, the polyphosphate concentration in the parts of the system where lead service lines occur may also have been seasonal, with a maximum in winter.