Hal touched the issue of limit values for indoor air and for emissions into indoor air in his comment on TVOC of Dec 31. Just some explanations.
Typcially toxicological studies form the basis, resulting in a maximum dose per 70 kg (or similar) that does not not cause any harm to a healthy human being. Occupational exposure workplace limit (OEL) is derived from that assuming maximum 8h/day and 40 h/week exposure and no exposure in between. Indoor exposure air limits are derived from the same data with additional safety factors. These factors are in Germany and in France: Factor 10 for longer exposure than 40h/week, and another factor 10 for including more sensitive population such as children, old people and those with impaired health. A third safety factor 10 is applied to suspected carcinogens - proven carcinogens are having much lower limit values. This exercise includes therefore starting with well documented OEL value, then division by 100 or 1000. At the end, the result is compared with any further documentation on indoor air related exposure-health relationship and possibly the final value is modified accordingly. These are the European so-called "Lowest concentrations of interest (LCI)" whereof both Germany (AgBB) and France (AFSSET) each have some 150-200 LCI limit values. For some lists and comparisons please see: www.product-testing.eurofins.com/lci-cli-nik-crel.aspx.
Also CRELs are developed in a similar manner, as you can see e.g. on page 24 of this paper: http://www.oehha.ca.gov/air/hot_spots/pdf/122010CaprolactamRELSRP.pdf.
We expect that there will appear many more "DNEL" (derived no effect level) limit values for long-term inhalation consumer exposure under REACH legislation, but this will certainly take some more years.
Differences between different lists of limit values come from (a) different toxicological data basis of the national OEL limit values, and (b) different indoor air limit values available.
Most prominent example of differences in indoor air limit values is the dispute on formaldehyde where WHO and Germany say that cancer risk with this special nasal cancer does not support same low limit values as for other carcinogenic substances because this cancer has a certain threshold dose, while California and France go for extremely low formaldehyde limit values assuming that no safe threshold can be postulated.
Brian Englert
Manager of Science and StandardsGREENGUARD Environmental Institute
29 thumbs up
January 3, 2011 - 10:18 am
Hal, I think that you are missing several of the points others have made. I think Reinhard has addressed several of your comments in his most recent post but let me address several others here.
It is interesting that I only brought up PCBs in one sentence, yet you have written nearly half a page on it here. I bring up PCBs because they are somewhat comparable to this situation for several reasons (you seem to agree on at least that much), however there are several points I think you have missed.
It isn’t correct to simply say “Analysis is done by specific congener.”
While PCBs can be measured as congeners, they are frequently measured as arochlor mixtures, especially in some regulatory settings. Various EPA methods are commonly used to measure PCB arochlor mixtures 1016, 1221, 1232, 1242, 1248, 1254, 1260 in soils.
Often, you find that arochlor methods are used when other congener specific methods could have been used, even though risk assessment moved to a congener specific approach years ago. That why this is a good comparison. Again, there are various reasons why one would use an arochlor or a congener specific method; data quality objectives, project goals…. this list could be long but it all relates to looking at what your end goals are.
While it would be preferable to measure all 209 PCB congeners, 209 is a more manageable number than the all the possible chemicals that could be found across the wide variety of products used in the indoor environment.
Again, I’d have to come back to my main points here: 1) TVOC can be used as a criteria with other available criteria for IVOCs and 2) the current criteria list being suggested cover a small number of chemicals found in indoor air. Given the extensive work required to develop additional list and risk based limits, TVOC is a practical approach to this issue.
Brian Englert
Manager of Science and StandardsGREENGUARD Environmental Institute
29 thumbs up
January 3, 2011 - 10:46 am
I want to simplify this jargon for those who don’t have time to read the long posts on this complicated issue. Think about it like this, do we want to measure only 35 chemicals when we know there are many more out there or do we want to measure 35 and use TVOC to cover chemicals outside of the 35 chemicals.
My main reasons for suggesting TVOC be used are: 1) TVOC can be used as a criteria with other available criteria for IVOCs and 2) the current criteria list being suggested cover a small number of chemicals found in indoor air. Given the extensive work required to develop additional list and risk based limits, TVOC is a practical approach to this issue.
Reinhard Oppl
Independent consultant on VOC issuesformerly with Eurofins Product Testing A/S
329 thumbs up
February 10, 2011 - 6:23 am
Let me add another thought - this time only regarding health risks from chronic inhalation exposure indoors. These will typically deal with dose-depending systemic effects, not so much with concentration depending local effects.
EMISSIONS DECAY
Emissions of volatiles from products into indoor air typically show an elevated level during some hours, days or weeks (depending on the respective product), and then they reach a level with very low decay, sometimes nearly steady-state emissions, over a longer time.
Emissions of semi-volatiles behave in a similar manner with the exception that these show a slower increase and a later maximum peak of emissions - if the semi-volatiles first have to diffuse from an inner layer to the surface then this maximum may be seen even after 3 - 5 weeks, in other cases already after some days.
TOXICOLOGY
Toxicological background for any other limit values dealing with health risks from chronic inhalation exposure will relate to much longer periods than the first 2 or 4 weeks. Any limit value for product emissions, such as ½ CREL or LCI, will refer to such long-lasting exposure level.
Any low VOC program using such limit values just assume that the period of emissions with very low decay would be reached after 7 days (GG), after 2 weeks (CA 01350 and BIFMA), or after 4 weeks (EU). The height of those limit values is not related to 7 days or to 2 weeks or to 4 weeks, it is related to long-term exposure levels. The testing after 7 days or after 2 weeks of after 4 weeks was selected only for saving time and costs for testing, not at all for toxicological reasons.
THIS MEANS THAT …
… if you test long-term emissions at whatever time, after 7 days or after 2 weeks or 4 after weeks, you can in fact apply any of those limit values for chronic inhalation exposure. In other words, you can apply CREL and/or LCI values to long-term emissions, independent of after which elapsed time whether you assume long-term emissions level can be evaluated. European carpet industry does this even more extremely: They assume long-term emissions level is reached already after 3 days for European textile floorings, and they apply the long-term limit values (LCI, TVOC etc.) already after 3 days for their low VOC program (PRODIS/GUT), saving testing time while accepting more stringent requirements than it is normal for other products. Similar approach is followed by Blue Angel regarding textile floorings.
In consequence, if we European LCI values would included in low VOC emissions evaluation along with ½ CREL values, then this could be done either for testing after 7 days or after 2 weeks or for testing after 4 weeks or any other testing period just if we assume that at that point of time we can see the long-term emissions level. In contrast to my earlier saying we would not need to estimate emissions decay behavior for this purpose, working with 2 x LCI if tested after 2 (not 4) weeks or ½ of ½ CREL if tested after 4 (not 2) weeks. We just can apply those limit values as they are, if we assume that we see the long-term emissions level at the testing date.
If that assumption is wrong, then we should rather consider testing at a later date in order to evaluate long-term emissions and nothing else.