The maximum substitution of monovalent, divalent, and trivalent metal ions for b-tricalcium phosphate (b-TCP) was investigated, and a substitution model of these metal ions for b-TCP was proposed. Monovalent metal ions (M I ) could replace Ca(4) site and vacancy (V Ca (4) ) in b-TCP as 2M I 5 Ca 21 1V Ca(4) and the maximum substitution was about 9.1 mol%. In the case of divalent metal ions (M II ), Ca(4) and Ca(5) sites were replaced by divalent metal ions as M II 5 Ca 21 , and the maximum substitution was about 13.6 mol%. Trivalent metal ions (M III ) could be substituted for Ca(4) site and vacancy as 3M III 5 2Ca 21 1V Ca(4) , and the maximum substitution was about 9.1 mol%.

No abstract

Humans are exposed to ubiquitous phthalates via multiple pathways. Exposures to phthalates have been estimated in some previous risk assessments in Japan based on point-of-contact measurement or scenario evaluation approaches. While the Japanese national government has regulated the use of di(2-ethylhexyl)phthalate (DEHP) and excluded several other phthalates from its regulation based on some of them, it is unclear whether such past exposure assessment studies fully assessed total human exposure to phthalates. In the present study, we measured their urinary metabolites, which show direct evidence of human exposure to phthalates. We recruited voluntary participants (N = 36) who agreed to donate urine samples, and measured the urinary concentrations of phthalate metabolites using enzymatic deconjugation, solid-phase extraction, and high-performance liquid-chromatography isotope-dilution tandem mass spectrometry. We then derived the daily intakes of their respective phthalates based on steady state assumption and finally compared them with the corresponding estimated daily intakes of each phthalate via diet and air derived from previous exposure or risk assessments in Japan. These comparisons showed that exposures to dimethyl phthalate, diethyl phthalate, and di-n-butyl phthalate via diet and air accounted for less than half of their respective total exposures. On the other hand, it appears that dietary intake was more predictive for the total exposure to n-butyl-benzyl phthalate and DEHP. The probabilities that the log normal distribution of each phthalate daily intake estimated from the present study exceeds the corresponding tolerable daily intake were estimated to be less than 10(-4).