I agree with Tammy. From what I have read there are a lot of PAH's out there that are highly carcinogenic (some of the methylated forms of Chrysene for instance seem to be quite nasty), but are not routinely looked for in samples. It would also appear that the methylated forms of most PAH's are more carcinogenic than the none methylated forms as well (will these be picked up in the analysis techniques used?!). I am not advocating that we test for every PAH known to man due to the costs of this, however a pragmatic approach needs to be adopted in determing which PAH's should be looked for. We have the USEPA 16, and noone I have spoken to has a list of the Second Site 19 (unless someone out there has it and are willing to distribute it to the list); but are these lists necessarily correct?
However, as Tammy says a paucity of biological data as well as chemical fate and transport data hampers in the modelling of these, as well as deriving MDI/TDI's etc. It would be interesting to know where the Agency are with the TOX reports for threshold and non-threshold PAH's, and on what basis they are using to decide which PAH's need to be assessed (I am assuming they will be looking at those as listed in the draft P5-079/TR1 report). This I am sure would help remove some of the uncertainty on which PAH's to look for (I hope anyway!).
A handy document I have found is an assessment of PAH's by the EU's Scientific Committee on Food (hyperlink provided at end of email), which summarises most of the research on PAH's up to 2002.
However, in assessing the carcinogenicity of PAH's, this would really seem to leave us with Toxic Equivalency Factors. It seems though that TEF's are unreliable as based scientifically, they can only really be used on those chemicals that have the same mechanisms for their carcinogenicity causing properties (see one of the Appendices to the hyperlinked document). In the light of nothing better though and a lack of data what else are we to do?
As a Regulator it concerns me that we may be missing PAH's that may need to be assessed because they are not on a list; as someone living in the real world where time is money is this a practical approach and is there sufficient risk to warrant investigating them?!
I suppose knowing what the mechanisms of certain PAH production are (incomplete combustion methods etc.) would help to provide us with a means to determine what may be found on a site by site basis. If they are all produced the same way where does this leave us?
Leaving aside the problem of PAH mixtures (which is also discussed in the document), what are we to do? I am sure there are Members of the list who are far more versed in the technical implications of this.
I am soon to begin looking at an old Landfill under Part IIA; the fill was deposited in the 1950's and covers the time of the Clean Air Act so I will have a mix of ashy waste as well as more putrescible waste. If all (or most) PAH's are produced in a similar way; then do I look for them all; do I selectively choose those in the literature that are most genotoxic, do I ignore the ones not on the USEPA 16 list? Do I just look for those that can be produced in the combustion of organic material? (atmospheric deposition anyone?) Do I just bury my head in the sand and hope it all goes away?
This then gets me onto dioxins etc................................................!
I have a headache now!
Jon
http://europa.eu.int/comm/food/fs/sc/scf/out154_en.pdf
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]]On Behalf Of Tammy
Sullivan
Sent: 17 March 2006 09:59
To: [log in to unmask]
Subject: Re: USEPA16 PAH's
My humble opinion is that any list has problems from a risk assessor's or
regulator's view point if the compounds that are on it have limited or no
toxicological data. Some of the issues that are currently creating
difficulty are that site investigations and laboratories can generate data,
but then risk assessors and regulators are left struggling to use and
interpret the data appropriately, and then make decisions regarding clean up
which is both protective of human health and the environment and fiscally
responsible.
I don't advocate sticking our heads in the sand and not addressing the
problems of contaminants, but I also believe it is not responsible to be
crying wolf. Oh what a tangled web we weave for ourselves.
Tammy Sullivan
Principal Environmental Engineer
Earth Sciences
on behalf of RoC Consulting
81-83 Chapel Street
Manchester M3 5DF
Telephone 0161 839 2233
Fax 0161 839 2244
[log in to unmask]
http://www.rocconsulting.com
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-----Original Message-----
From: Jonathan Parr [mailto:[log in to unmask]]
Sent: 16 March 2006 08:42
To: [log in to unmask]
Subject: USEPA16 PAH's
Hello all!
I want to start a debate on the use of the USEPA16 PAH list and its
potential to be replaced with a UK list (I haven't seen a copy of the Second
Site 19 list so cannot comment on it).
I wonder what people think about the current list, what could be removed,
what could be added, and so on!
Jon
Jonathon Parr
Public Protection Officer [Contaminated Land]
Environmental Protection
Environmental Services
Blackpool Borough Council
125 Albert Road
Blackpool
FY1 4PW
[log in to unmask]
Tel: (01253) 478318
Fax: (01253) 478396
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