http://www.atsdr.cdc.gov/hac/pha/pha.asp?docid=1036&pg=0
This is a Public Health Assessment conducted in 1996-97 by the CDC Agency for Toxic Substances and Disease Registry (ATSDR).
Firstly, this is not a health study, which the CDC is quick to point out. (Give them a call if you want to confirm - plenty of helpful folks both in Atlanta and Region 9). Health studies tend to focus on observed health issues and then possible causes. This assessment focuses instead on a single compound, H2S, the levels detected, and possible health implications.
It is a quick read, but I would summarize it like this: Given the levels of H2S detected from Jan 1996 - Apr 1997, there appears to be no related public health hazard in the PGV area given our current knowledge of exposure to H2S.
A few thoughts on the assessment:
1) Data for H2S levels gathered may be insufficient or unrepresentative. The H2S levels were taken from air monitors located in Leilani and Lanipuna, and compared to the 3 air monitors on site at PGV. Another air monitor was (generally) upwind at Lava Tree to gather ambient H2S readings. It may be that these gathering areas may not well represent the area, given differences in winds, vegetation, low-lying terrain, etc.
A clear example of the difficulty of gathering consistent data on H2S levels can be seen during the March 13, 2013 release event at PGV.
- 1 monitor at PGV shows a peak of 1ppb at 4PM. The other 2 monitors registered no change at all.
http://72.253.107.171/graph/ H2S Data: 2013 - 3 - 13 - View Day
- As PGV went around the plant, Mike Kaleikini said they registered levels as high as 25 ppb and that a monitoring station registered a 19 ppb peak H2S level (16.7 ppb 5 minute average).
https://www.youtube.com/watch?feature=player_detailpage&v=Y33k7aFXHao#t=410
- Darryl Oliveira said hand-held monitors registered peak H2S levels of 1000 - 3000 ppb in the surrounding subdivisions.
https://www.youtube.com/watch?feature=player_detailpage&v=6nuxSxS-jIE#t=41
Differences in time, location, winds, and topography resulting in wide differences in peak H2S levels recorded.
2) The data was not independently gathered by the CDC. H2S data was provided by the Hawai'i Dept of Health. Given the clear and wide-ranging political interest in expanding geothermal, it's probably of value to have data gathered by outside agencies, such as the EPA, whose appointments and purse-strings are not subject to local political pressure, if only to avoid the appearance of a potential conflict of interest.
3) Natural background levels of H2S appear to be at similar low levels to that of PGV. For those who point to natural H2S emissions as the source of possible health issues, the ATSDR assessment appears to discount that possibility as well. However, possible sampling issues, as noted in 1), may play a role here as well.
4) The understanding of chronic of exposure to H2S has improved since 1997.
As this assessment is 18 years old, the conclusions may be dated and subject to revision by newer findings. The ATSDR is updating their toxicological profile for H2S and now includes information on their Medical Management Guidelines for Hydrogen Sulfide (H2S) such as:
http://www.atsdr.cdc.gov/mmg/mmg.asp?id=385&tid=67
"Hydrogen sulfide does not accumulate in the body. Nevertheless, repeated or prolonged exposure has been reported to cause low blood pressure, headache, nausea, loss of appetite, weight loss, ataxia, eye-membrane inflammation, and chronic cough. Neurologic symptoms, including psychological disorders, have been associated with chronic exposure. Chronic exposure may be more serious for children because of their potential longer latency period."
To understand why, we'll need to look at some of the actual health studies done.
