M I N N E S 0 T A MDH
DEPARTMENT of HEALTH
Memo
Date: February 15, 2000
To: Greg Ruff
Minnesota Pollution Control Agency
From: Kathy Norlien, Health Risk Assessment Unit
Division of Environmental Health
Subject: Review-of Hydrogen Sulfide Data ValAdCo
(Finishing
Site, Section 27, Norfork Township, Renville County, MN)
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At the request of the Minnesota Pollution Control Agency (MPCA), the Minnesota Department of Health (MDH), Health Risk Assessment Unit, has completed review of monitoring data collected from the ValAdCo finishing site in Renville County, Minnesota. The data reviewed includes 1) 1998 data for hydrogen sulfide collected from April 6, 1998 through September 24, 1998, and 2) 1999 report for days where hydrogen sulfide concentrations were greater than or equal to 30 ppb (at least one 30 minute average per day). The 1999 data were collected between June 12th and September 15th.
In summary, MDH believes that monitored levels are high enough to pose a potential threat to human health. After consideration of the data collected and the circumstances involving the emission source, MDH believes that, for the protection and well being of human health, without delay, action should be taken to reduce the emissions of hydrogen sulfide and bring hydrogen sulfide emissions back in compliance with Minnesota Rules 7009.0080.
The standards and guidance described herein, have been written for the
purpose of protecting human health and the quality of life for Minnesotans.
This paper provides health-based guidance for hydrogen sulfide and summarizes
the findings of monitoring performed at the fence line of the ValAdCo finishing
site.
MDR Draft Health Risk Values (URVs) for Hydrogen Sulfide
MDH is in the process of proposing two draft Health Risk Values (HRVs) for exposure to hydrogen sulfide. The draft MDH RRVs, outlined below, differ substantially from the MPCA state ambient air quality standard for hydrogen sulfide based on a mean odor detection limit. The MPCA state ambient air quality standard for hydrogen sulfide protects against physiological symptoms of headache and nausea and also addresses quality of life issues for Minnesotans.
Division of Environmental Health 121 7Th Place,
St. Paul, MN 55102
(651) [215-0700] http://www.health.state.mn.us
Greg Ruff
Page 2
February 15, 2000
Acute
The draft acute HRV is based on a study by Jappinen et al1 that found changes in lung function manifested by an increase in mean airway resistance (SRaw) and a decrease in mean airway 113 conductance (SGaw) of subjects exposed to hydrogen sulfide. The draft acute HRV is 80 µg/m3 or 60 ppb, and is notably higher than the mean odor threshold (42 µg/m3 ) for hydrogen sulfide. As further described in an MDH briefing paper, M.DH believes it is necessary to have an acute HRV for hydrogen sulfide based on rcspiratory system implications. To protect sensitive populations, an uncertainty factor of "T' was used in calculating the acute draft RRV. This uncertainty factor is used to account for consideration that the study group was not representative of a truly sensitive population and for protection against possible developmental effects previously demonstrated in rodent studies. The acute draft HRV is not intended to replace the quality of life standard, but rather would complement the standard already set by MPCA.
Subchronic
In addition to a draft acute HRV, MDH is intending to propose a subchronic HRV based on 90-day inhalation studies using B6C3F1 mice (CIIT, 1983a) and 90-day vapor inhalation studies conducted using Sprague-Dawley and Fischer 344 rats (CIIT, 1983b,c). The toxic effect found in these studies was inflammation of the nasal mucosa. The draft subchronic HRV for hydrogen sulfide is 10 µg/m3 or 7 ppb.
1998 Monitoring Results
The Minnesota state standard allows two exceedences per year of the thirty minute average of 50 ppb. Monitoring data collected between April 6, 1998 until September 24, 1998, showed that there were fifty three 30-minute averages that exceeded 50 ppb. Fourteen of the half-hour averages were greater than or equal to 90 ppb, the upper detection limit of the monitoring equipment. Monitored results of concentrations greater than 90 ppb are recorded as 90 ppb. Therefore, the emissions for these fourteen 30-minute averages remains unknown.
To compare the monitored data with the MDH draft acute HRV for hydrogen sulfide, one needs to examine exceedences that occur on an hourly basis. During a period of approximately 3 months, from April 30, 1998 through July 11, 1998, the one hour acute draft HRV value of 60 ppb was exceeded a total of eight times.
A quarterly (three month) analysis of data collected from 1998 show
an average of 6 ppb or greater of hydrogen sulfide for the three month
period including June, July and August. This is a conservative average
because at least five of the values were greater than or equal to 90 ppb.
As
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1 Jappinen, Vilkka, Marttila, and Haahtela, Exposure
to hydrogen sulphide and respiratory function, published in the
British Journal of Industrial Medicine, 1990; 47:824-828.
2 Minnesota Department of Health. Briefing Paper #12, Hydrogen Sulfide. Spring 2000 (in progress).
[Division of Environmental Health] [121 E. 7th Place]
[St. Paul, MN 55102] (651) [215-0700]
http://www. health. state. mn. us
Greg Ruff
Page 3
February 15, 2000
stated above, the equipment could not provide accurate readings of monitored
hydrogen sulfide concentrations over 90 ppb. The actual average concentration
of hydrogen sulfide for these months could very well have exceeded the
draft subchronic HRV of 7 ppb.
1999 Monitoring Results
In September of 1998, the basins at ValAdCo were covered with straw. Limited monitoring results from the following year were provided to MDH. MPCA provided monitoring data where at least one reading on any given day exceeded 30 ppb. The monitoring data collected from 1999 did not include days on which little or no hydrogen sulfide was picked up by the monitors, therefore, a quarterly average could not be calculated as done with the 1998 monitoring data.
Analysis of the 1999 data show 106 exceedences of the 50 ppb MPCA standard- twice the number found the previous year. A total of 86 half hour averages were greater than or equal to 90 ppb. Once again, the monitors were unable to register readings above 90 ppb. On September 25, 1999, over six hours in one day had levels greater than or equal to 90 ppb.
At a minimum, thirty two hourly averages exceeded the 60 ppb MDH draft
acute HRV for hydrogen sulfide. During a 10-day period from July 19, 1999
through July 28, 1999, there were at least 25 hourly exceedences of the
60 ppb draft acute HRV for hydrogen sulfide.
Additional Considerations
The data from the ValAdCo facility provide MDH with a good overview of hydrogen sulfide emissions recorded during the past two summers (1998 and 1999). Although all of the data were not available for review, the existing data indicates that hydrogen sulfide concentrations near the monitor provide evidence for potential adverse health effects due to hydrogen sulfide concentrations.
Monitoring data and calculated exceedences of health benchmarks are conservative. MDH counted only cases where there were clear cut exceedences of the draft HRV or state H2S standard. For hourly averages, an exceedence was not included unless both 30-minute values exceeded 60 ppb. Many more exceedences may have occurred. Exposures to hydrogen sulfide often continued even during times where the ambient air standard or draft HRV was not being exceeded.
As stated earlier, the 1998 three month average hydrogen sulfide monitored concentration was 6 ppb, very close to the 7 ppb draft subchronic HRV for hydrogen sulfide. MDH was unable to calculate a quarterly average for 1999, although, considering the monitoring data provided to MDH, the 1999 quarterly average generally had higher monitored values than in 1998. MDH expects that the 1999 data for June, July and August would exceed the draft subchronic HRV.
[Division of Environmental Health] [ 121 7th Place],
[St. Paul, MN 55102] (651) [215-0700]
http://www.health.state.mn.us
Greg Ruff
Page 4
February 15, 2000
Finally, hydrogen sulfide is only one of the many chemicals emitted to air by feedlots. Ammonia and other irritant emissions were not monitored. The monitors primarily measure hydrogen sulfide emissions and although other reduced sulfur compounds are not expected to comprise a large portion of the emissions, they may be present and adding to the effects of hydrogen sulfide.
Summary
In summary, MDH believes that monitored concentrations are high enough to pose a potential threat to human health. Monitored concentrations of hydrogen sulfide indicate that emissions from the ValAdCo facility are high enough to cause nausea and headaches and interfere with the quality of life of nearby residents. In addition, monitored concentrations indicate that the health-based draft acute HRV is exceeded on a regular basis and is close to, or may exceed the draft subchronic HRV.
After consideration of the data collected and the circumstances involving the emission source, MDH believes that, without delay, action should be taken to reduce the emissions of hydrogen sulfide and bring hydrogen sulfide emissions back in compliance with Minnesota Rules 7009.0080 for the protection and well being of human health.
cc: Jim Sullivan, MPCA
Rick Strassman, MPCA
KN:rlk
[Division of Environmental Health] [121 E. 7th Place], [St. Paul, MN
55102] (651) [215-0700]
http://www.health.state.mn.us