Arvin air sample, and independent interpretation, Nov 20th 2017

20 November 2017

Central California Environmental Justice Network (CCEJN)

930 Truxtun Ave Ste. #113

Bakersfield, CA 93301


RE: Public Health and Environmental Significance of VOC levels in Ambient Air at the Intersection of Towner Drive & Nelson Court in Arvin, California

The Central California Environmental Justice Network (CCEJN) asked that I provide an expert opinion about the public health and environmental significance of levels of volatile organic compounds (VOCs) in a sample of ambient air that was collected at the intersection of Towner Drive & Nelson Court in Arvin, California, at around 7:00 p.m. of October 30th, 2017.  In my opinion, if the levels of VOCs in the sample reflect generally prevailing conditions, then they represent exposure of residents to levels of benzene that pose an unacceptable risk of cancer and decreased peripheral blood cell counts.  The source of such unsafe levels of benzene is most likely a leakage of methane and natural gas liquids from an oil & gas storage facility approximately 150 feet southeast of the residential area.

Methane and natural gas liquids (ethane, propane, butane, isobutane and pentane) are a family of small-chain volatile hydrocarbons found in prevalent commercial fuels.  The sample of ambient air that was collected at the intersection of Towner Drive & Nelson Court in Arvin, California, at around 7:00 p.m. of October 30th, 2017, contained the following levels of methane and natural gas liquids:[1]

Compound Concentration µg/m3
Methane 21900
Propane 1,500
Isobutane 1100
n-Butane 1400
2-Methylbutane 750
n-Pentane 480

These levels of methane and natural gas liquids vastly exceed naturally-occurring levels.  For example, present-day levels of methane, a well-studied greenhouse gas, are only 1270 µg/m3 (1.8 parts per million) in ambient air unaffected by a source of VOC pollution.

Benzene is a volatile aromatic hydrocarbon associated with methane and natural gas liquids that are commercial fuels.  Benzene is a known human carcinogen.  Exposure to benzene is also known to cause non-cancer health effects, including adverse impacts to the human immune systems and the formation of blood cells.  The California Office of Environmental Health Hazard Assessment (OEHHA) has determined that the lifetime tumor risk associated with continuous inhalation of benzene is 29 per one million for each incremental increase of 1 µg/m3.[2]  The California Office of Environmental Health Hazard Assessment has also established a safe annual average concentration of benzene in ambient air of 3 µg/mto prevent decreased peripheral blood counts in exposed individuals.[3]

The level of benzene collected at the intersection of Towner Drive & Nelson Court in Arvin, California, at around 7:00 p.m. of October 30th, 2017, was 15 µg/m3 .     If this is the generally prevailing level of benzene at this location, then it represents an unacceptable lifetime cancer risk of 435 per million exposed individuals.  It also represents a level that is 5 times the level established by OEHHA to prevent decreased peripheral blood counts in chronically exposed individuals.

The comments on the Chain of Custody Record state “Visible Pipeline Leakage (Photo Avail).”  It is my understanding that the photo below is of the pipeline leakage that was observed at the oil & gas storage facility approximately 150 feet southeast of the residential intersection.

The contemporaneous observation of pipeline leakage from the oil & gas storage facility is substantial evidence that it is the source of methane, natural gas liquids and benzene that was found in the sample of ambient air that was collected at the intersection of Towner Drive & Nelson Court in Arvin, California, at around 7:00 p.m. of October 30th, 2017.

The high levels of methane and natural gas liquids in the sample of ambient air collected at the intersection of Towner Drive & Nelson Court also represents a possible risk to public safety.  The lower explosive limit (flammability point) of methane and natural gas liquids is between 2-5% by volume of air.   Combined levels of methane and natural gas liquids in the sample of air at the intersection of Towner Drive & Nelson Court were approximately 30,000 µg/m3, equivalent to a concentration by volume of air of approximately 0.005%.  If the oil & gas storage facility is indeed the source of these VOCs, then levels of methane and natural gas liquids would be exponentially higher in air that is nearer to the leakage, raising the concern of whether VOCs exist at levels at which a source of ignition (e.g. a spark) could cause a damaging explosion.

Please let me know if you have any comments or questions.

Sincerely,

Mark Chernaik


[1] Ethane levels were not quantified but are assumed to be present at a concentration intermediate  that of methane and propane.

[2] California Office of Environmental Health Hazard Assessment “Hot Spots Unit Risk and Cancer Potency Values.” https://oehha.ca.gov/media/CPFs042909.pdf

[3] California Office of Environmental Health Hazard Assessment (July 2014) “Technical Support Document for Noncancer RELs ”  https://oehha.ca.gov/media/downloads/crnr/appendixd1final.pdf