When visualizing data that has <1 or <5 ppm how do you display this? I have some data (parts per million) where some of it is 1 or greater than one (but has an actual number.) However, some of the data simply lists "&lt;1" ppm.

What is a good way to visualize this in a graph?

Should I pick an arbitrary decimal less than one, so that it can be shown on the graph? I feel setting it to zero would not be right either, as they went to the extent of listing it, so it must be significant.
Is it a univariate plot?  If so, just bin the data and toss it into the lowest bin.