[MHGinTN]

You make a false assumption, that the material of the star would be evenly ejected and have no clumping.

[lmr]

You make a false assumption, that the material of the star would be evenly ejected and have no clumping.

There wouldn't be any clumping at all. Imagine a Fusion Nuclear blast 10 times the scale of our sun. The blast wave would eject the particles in an even manner and disperse them quickly. Even if there was 'clumping', that would be diminished quickly in our atmosphere unless the 'clumps' were very large to make them asteroid size which would be even more catastrophic than even what this article is suggesting.

Type la supernovae would be the most dangerous if close enough to the earth because they arise from dim (almost black) white dwarf stars. For there to be any effect on the earth they would have to happen fairly close to the earth. 25-50 light years away. At that distance, they may deplete the ozone layer, but would even need to be closer than that for higher radiation and particle bombardment on the scale that this article is suggesting.