<Tr> <Th> Substance </Th> <Th> RDA / AI </Th> <Th> UL </Th> <Th> units per day </Th> </Tr> <Tr> <Td> Arsenic </Td> <Td>--</Td> <Td> ND </Td> <Td>--</Td> </Tr> <Tr> <Td> Silicon </Td> <Td>--</Td> <Td> ND </Td> <Td>--</Td> </Tr> <Tr> <Td> Vanadium </Td> <Td>--</Td> <Td> 1.8 </Td> <Td> mg </Td> </Tr>

In the united states and canada what set of standards defines the recommended