But, that's not what you asked:
"would a drop in that number to three be statistically significant?"
That phrase "statistically significant," is well-defined and understood in statistics.
Because, presumably, you have only a single data point, it may or may not be statistically significant, because, even if it is grossly out of the norm, it may well be a fluke; as alluded to by others, your plant's "Typhoid Mary" or "Martin" may have missed days for other reasons.
Even in your latest posting, significance can still be asked from a statistical perspective. You posit some number of explosions in a specific month, March, but presented no data for either location. Without the data, you cannot statistically demonstrate significance.
Likewise in your original posting and subsequent ones, you still have not presented any background to your numbers, hence, there can be no conclusion drawn from a statistical perspective.
TTFN