As discussed in the above post, I have recalculated a comparison between sites assuming a log-normal distribution.

After some further reading and consideration I decided that using a normal distribution to compare sites was problematic as there are some very small emissions and very large ones. In order to linearise the data I took the natural logarithm of each emission, calculated the Z-scores using the sample mean and standard deviation, then summed exp(Z) for each site and medium (air, direct water, indirect water). I believe this provides a much more accurate means of comparing sites.

The updated collection has been added to the original post. I have also changed the way I have highlighted large emissions. These are emissions greater that 1.645 times the standard deviation. This is equivalent to the top 5%.

On this basis, the top 20 European pollution emitters are:
ILVA S.P.A. - TARANTO, Italy (Metal industry)
U.S.Steel s.r.o., Slovakia (Metal industry)
NOVACARB - LANEUVEVILLE-DEVANT-NANCY, France (Basic inorganic chemicals or fertilisers)
KEMIRA GROWHOW UK LTD - CHESTER, United Kingdom (Basic inorganic chemicals or fertilisers)
Zakady Chemiczne POLICE SA - Police, Poland (Basic inorganic chemicals or fertilisers)
Mittal Steel Ostrava a.s. - Ostrava, Czech Republic (Combustion installations > 50 MW)
ASSOCIATION OF LOCAL AUTHORITIES OF GREATER THESSALONIKI - , Greece (Disposal of non-hazardous waste and landfills )
Aluminium Pechiney Usine de Gardanne - GARDANNE, France (Metal industry)
BASF Gruppe - Ludwigshafen, Germany (Basic inorganic chemicals or fertilisers)
Narva Elektrijaamad AS - Vaivara vald, Estonia (Combustion installations > 50 MW)
Zakady Górniczo-Hutnicze S.A - Bukowno, Poland (Metal industry)
PPC S.A, SES AGIOY DHMHTRIOY, Greece (Combustion installations > 50 MW)
AB "Kaisiadoriu paukstynas" - Kaisiadorys, Lithuania (Poultry, pigs and sows )
voestalpine AG - Linz, Austria (Metal industry)
MITTAL STEEL POLAND S.A. - Dbrowa Górnicza, Poland (Metal industry)
YARA Sluiskil BV - SLUISKIL, Netherlands (Basic inorganic chemicals or fertilisers)
SOLVAY QUIMICA S.L. - CANTABRIA, Spain (Basic inorganic chemicals or fertilisers)
NTG (Paper Mill) Ltd - LANCASTER, United Kingdom (Pulp, paper or board production)
SIDMAR - Sint-Kruis-Winkel, Belgium (Metal industry)
Brunner Mond B.V. - Delfzijl, Netherlands (Basic inorganic chemicals or fertilisers)