hello everybody my name is Zohir Chowdhury, and today's topic is CERCLA priority list of
hazardous substances so hazardous waste site in the US this map that's where we're seeing we're
seeing different location around the US that shows the Superfund sites that we discussed earlier and
the Superfund sites are in blue then we are seeing the current rikiya sites in green and
then in brown we are seeing the brownfield sites so what are these brownfield sites essentially
there are about 40,000 hazardous waste sites that have been reported to federal agency and
brownfield sites are sites they're abandoned closed or under used industrial commercial
facilities such as an abandoned factory in a town's former industrial section or a closed
commercial building or warehouse in a suburban setting in many of the cases brownfields have
used hazardous waste hazardous hazard chemical and potentially they may be hazardous in nature
so they need to be watched in here super funds as we mentioned earlier are sites that are have been
and to be remediated for hazardous chemicals and Rick recites are those sites that have a
hazardous spills and our active sites that need to be cleaned that they're getting cleaned up so
national priority list sites eligible for CERCLA this is a list that is a short list and these
shortlisted sites are known as national priority list these are locations where there there are
hazardous chemicals and they need to be cleaned up and they are eligible to be financed under
and as of 2014 1322 sites are within the national private lists and within these sites 375 have been
cleaned up already and 53:53 new sites have been proposed for inclusion and this map which we also
saw it earlier in red we are seeing the Superfund sites in yellow the proposed Superfund sites and
in green the cleaned up Superfund sites so certified a list of hazardous substances
essentially is a list of chemicals and there are about few hundred chemicals in this hazardous in
this priority list of hazardous substances it is put together by the agency for toxic substances
and disease registry or known as ATSDR and the top 20 hazardous chemicals are the most hazardous
for the in this list and this list of hazardous officer kumata list is revised every two years
and it is based on two main criteria whether the chemicals are featured have known or suspected
toxicity and the potential for this chemical for human exposure at the CERCLA or the national
priority list locations that I should rather be shown earlier based on these two criteria the
chemicals are ranked so if a chemical is extremely extremely toxic however the potential for exposure
is small then the ranking would make it go lower because both are important if a chemical has high
potential for exposure with medium to high toxicity then that chemical would definitely
rank much higher so based on these two criteria toxicity of the chemical and exposure to human
health in NPL location this is the top 20 list of chemicals ranked from the most harmful to the 20th
most harmful all of them are very dangerous in red you can see that in organic chemicals
arsenic lead mercury cadmium hexavalent chromium and phosphorus white and there are six of them
I highly recommend that you memorize this list not the ranking just that they are within the
top 20 vinyl chloride polychlorinated biphenyls benzene benzo a pyrene and as many other chemicals
including DDT are featured in this list as well and the black designate that they are organic
chemical chemically organic chemical so that was the list that I showed you was the list in 2000
like currently whereas in here in 2003 in the past this is how the list look like and if you notice
between the 2003 and the current list there has not been a lot of movement that means that this
chemical the exposure are still high and toxicity is well known so they still are within the top 20
most dangerous chemicals however as they as their exposure declines because of banning and half-life
decay they slowly start falling off the list as well okay alright so which substances moved up
or down the ranking from 2003 to present there's something that you definitely want to take a close
look at and see whether anything has moved and as I mentioned the movement is very minor these
twenty chemicals in here they can be categorized in many categories so arsenic lead mercury cadmium
excellent chromium and phosphorus they're all metals or elements they're inorganic in nature DDT
is a pesticides as most of you know or a klore as of the diode rain have been used as pesticides and
then you have industrial solvents such as benzene and trichloroethylene combustion by-product at the
benzo a pyrene polycyclic aromatic hydrocarbons benzo Florentine die benzo anthracene they're
all combustion byproducts and then some of the chemicals that are pesticide they are also used
as industrial applications such as the aura course chloroform vinyl chloride and pleura
my panels are also used in industrial applications so in here this list helps you to categorize the
list that you saw earlier into various categories so you can to help you remember them better okay
so let's do some quick conception hexavalent chromium is not on the result list of top 20
hazardous substances in the United States that's false it is an inorganic chemical and it is in
the list DDT is featured in the recent list of top 20 hazardous substances in the United States
that strew DDT is indeed featured in the top 20 list it is a pesticide and has been banned long
time back but exposure is very high in NPL sites that concludes our lecture for today