The basic results are also robust to a wide variety of specification
checks. SI Appendix, Tables S5 and S6 document that the
results are qualitatively unchanged by using alternative methods
to assign TSP concentrations to DSP locations. SI Appendix,
Table S7 shows that the panel 1 results are qualitatively unchanged
by expanding the sample to the full set of 144 DSP locations (with
valid mortality data) from the 125 locations with TSP data. Further,
the results are unchanged by adjustment for distance from
the coast (SI Appendix, Table S8).