KahuPuna Research files

Industrial geothermal operations, primarily power generation, can expose workers and nearby communities to various naturally occurring substances that become hazardous at higher concentrations due to extraction, processing, and disposal.

Here are the key industrial geothermal toxins and their health implications:

I. Gaseous Emissions and Inhalation Hazards:

The primary concern with industrial geothermal operations often revolves around the release of non-condensable gases (NCGs) from the geothermal fluid.

• Hydrogen Sulfide (H₂S):

  • Source: The most prevalent and problematic gas released from geothermal wells and power plants. It has a characteristic "rotten egg" smell even at very low concentrations.

  • Health Effects:

    • Low Concentrations (ppb to low ppm): Odor nuisance, eye irritation (conjunctivitis), headaches, nausea, dizziness, fatigue, sleep disturbances, and respiratory tract irritation (cough, shortness of breath). Studies have indicated that long-term exposure to concentrations as low as 20 ppb can be associated with increased respiratory symptoms and neurobehavioral changes in exposed populations. 

    • Moderate Concentrations (50-250 ppm): Severe eye and respiratory irritation, loss of smell, headache, dizziness, nausea, vomiting, and tremors.

    • High Concentrations (>500 ppm): Rapid unconsciousness, respiratory paralysis, pulmonary edema, cardiovascular effects, and death. H₂S is a chemical asphyxiant.

    • Relevant Studies: Numerous epidemiological studies have investigated communities near geothermal plants, linking chronic low-level H₂S exposure to increased prevalence of respiratory illnesses, headaches, fatigue, and other neurological symptoms. Occupational studies confirm acute and chronic effects on workers.

    • Mercury (Hg):

    • Source: Present in varying concentrations in geothermal fluids and can be released as elemental mercury vapor during power generation.

    • Health Effects: Primarily neurotoxic. Inhalation of elemental mercury vapor can lead to:

    • Neurological: Tremors, memory loss, insomnia, irritability, shyness, personality changes, motor dysfunction.

    • Renal: Kidney damage.

    • Respiratory: Pneumonitis (inflammation of the lungs) with acute high-level exposure.

    • Oral: Gingivitis (gum inflammation).

    • Relevant Studies: While less prevalent than H₂S studies, concerns exist regarding mercury accumulation in the environment around geothermal sites and potential human exposure, particularly in areas with higher natural mercury presence in geothermal fields.

    • Radon (Rn):

    • Source: A naturally occurring radioactive gas that can be present in geothermal fluids and released into the atmosphere during drilling and power generation.

    • Health Effects: Radon is a known human carcinogen.

    • Lung Cancer: Inhalation of radon and its decay products is the second leading cause of lung cancer after smoking. The alpha radiation emitted by radon decay products damages lung tissue.

    • Relevant Studies: Monitoring for radon emissions is a standard practice in geothermal environmental assessments. Studies have focused on assessing the risk to workers and nearby populations based on measured concentrations.

    • Benzene:

    • Source: Can be found in geothermal fluids, especially from sedimentary or metamorphic rock reservoirs.

    • Health Effects: A known human carcinogen.

    • Hematological: Primary concern is the link to leukemia (specifically acute myeloid leukemia - AML) and other blood disorders, including aplastic anemia.

    • Neurological: Acute high-level exposure can cause dizziness, headaches, and unconsciousness.

    • Relevant Studies: Research on benzene in geothermal fluids is critical, particularly for fields where its presence is detected, necessitating strict emission controls.

    • Other Gases (in smaller quantities):

    • Ammonia (NH₃): Can cause respiratory and eye irritation.

    • Carbon Dioxide (CO₂): While a major greenhouse gas, at very high concentrations (e.g., in enclosed spaces), it can act as an asphyxiant.

    • Methane (CH₄): A potent greenhouse gas; flammable but generally not directly toxic at ambient environmental concentrations.

    • Sulfur Dioxide (SO₂): Can be formed in the atmosphere from H₂S. A respiratory irritant that can exacerbate asthma and other lung conditions.

    • II. Water Contamination and Ingestion Hazards:

    • Geothermal fluids contain dissolved minerals and heavy metals. Improper handling, accidental spills, or inadequate treatment of spent geothermal brine can lead to contamination of surface and groundwater.

    • Arsenic (As):

    • Source: Commonly found in geothermal brines.

    • Health Effects (chronic ingestion):

    • Carcinogenic: Increased risk of skin, lung, bladder, and kidney cancers.

    • Dermatological: Skin lesions (hyperpigmentation, hyperkeratosis), "blackfoot disease."

    • Neurological: Peripheral neuropathy.

    • Cardiovascular: Hypertension, cardiovascular disease.

    • Relevant Studies: Studies in regions with high natural arsenic in groundwater (e.g., Taiwan, Bangladesh, Chile) illustrate the long-term health consequences of arsenic ingestion, providing a strong basis for concern regarding potential geothermal contamination.

    • Fluoride (F⁻):

    • Source: Naturally abundant in many geothermal fluids.

    • Health Effects (chronic ingestion):

    • Skeletal Fluorosis: Causes hardening of bones and joints, pain, stiffness, and potentially crippling deformities.

    • Dental Fluorosis: Discoloration and pitting of tooth enamel.

    • Relevant Studies: Areas with high natural fluoride in water sources demonstrate the link between chronic ingestion and fluorosis, highlighting the importance of managing fluoride in geothermal discharges.

    • Boron (B):

    • Source: Present in geothermal brines.

    • Health Effects (high ingestion):

    • Reproductive/Developmental: Animal studies show reproductive and developmental toxicity at high doses.

    • Gastrointestinal: Nausea, vomiting, diarrhea.

    • Relevant Studies: Research on boron's health effects primarily comes from occupational exposures or areas with high natural boron levels, indicating the need for careful management of geothermal discharges containing boron.

    • Lead (Pb), Cadmium (Cd), Chromium (Cr):

    • Source: Trace amounts can be present in geothermal fluids.

    • Health Effects: These are well-known toxic heavy metals with diverse adverse effects:

    • Lead: Neurodevelopmental effects in children, kidney damage, cardiovascular effects, anemia.

    • Cadmium: Kidney damage, bone demineralization, cancer (lung, prostate, kidney).

    • Chromium (hexavalent Cr(VI)): Carcinogenic (lung cancer via inhalation), skin irritation, kidney and liver damage.

    • Relevant Studies: Standard environmental toxicology applies. Monitoring and preventing the release of these elements from geothermal operations into water sources are critical.

    • III. Occupational Health Hazards:

    • Beyond the general environmental releases, workers in industrial geothermal facilities face direct and higher-level exposures to these toxins.

    • Acute Exposure: Risk of sudden high-level exposure to H₂S or other gases, leading to immediate severe health consequences or death.

    • Chronic Low-Level Exposure: Long-term exposure to airborne toxins and contact with geothermal fluids can lead to cumulative health effects as described above.

    • Physical Hazards: In addition to chemical exposures, occupational hazards include burns from high-temperature fluids, noise, mechanical hazards, and potential for silica exposure during drilling.

    • Key Considerations for Industrial Geothermal Toxins:

    • Geographical Variability: The specific suite and concentration of toxins vary significantly depending on the geological characteristics of the geothermal reservoir. Different fields will have different risk profiles.

    • Technology and Mitigation: The type of geothermal plant (e.g., flash steam, binary, dry steam) and the effectiveness of emission control technologies (e.g., H₂S abatement systems, re-injection of brine) play a crucial role in determining actual public and occupational exposure levels.

    • Monitoring and Regulation: Robust environmental monitoring, occupational health surveillance, and strict regulatory frameworks are essential to minimize exposure and protect human health.

    • Cumulative Effects: The combination of multiple toxins, even at low levels, can potentially lead to additive or synergistic health effects, which are harder to study but are an ongoing concern.

    • General Research and Resources for Industrial Geothermal Toxins:

    • Environmental Protection Agencies (e.g., US EPA): Provide guidelines and regulations for emissions and waste disposal from industrial facilities, including geothermal.

    • Occupational Safety and Health Administration (OSHA): Offers standards and guidance for worker safety and health in industrial settings, including geothermal.

    • World Health Organization (WHO): Publishes guidelines for drinking water quality and air quality, including limits for many of the toxins found in geothermal operations.

    • Scientific Journals: Journals focusing on environmental health, toxicology, geothermal energy, and public health frequently publish studies on the impacts of industrial geothermal operations. Keywords for search include "geothermal emissions," "hydrogen sulfide health effects," "arsenic geothermal," "geothermal environmental impact assessment."

    • National Academies of Sciences, Engineering, and Medicine (NASEM) Reports: May cover specific aspects of energy technologies and their environmental/health implications.

    • Understanding these specific industrial toxins and their potential health impacts is crucial for responsible development and operation of geothermal energy projects.