Chapter 3 Continued: What do we know about the potential health effects of exposure to landfill gas?
Landfill gas constituents are typically found in ambient air at low concentrations unlikely to cause adverse health effects. However, whether landfill emissions pose a health hazard depends on the chemical concentrations to which people are being exposed and the duration of the exposure.
In addition to concerns about persistent landfill gas odors, people living near a landfill may be concerned about the health effects of exposures to the landfill gas mixture or specific landfill gas constituents, both in the short term and in the long term. As described below, odor-producing chemicals (i.e., hydrogen sulfide and ammonia) are not likely to produce long-term adverse health effects at the levels typically associated with landfill emissions. The odors associated with these chemicals can, however, cause acute (short-term) effects, such as nausea and headaches, as mentioned earlier. Acute effects from other chemicals found in landfill gas are usually produced only when an individual is exposed at relatively high concentrations (i.e., at concentrations greater than those expected to be present in ambient air near a landfill). Acute effects are usually reversed when the odor or exposure ends.
- Hydrogen sulfide. To date, researchers
have not identified any long-term health effects associated
with exposure to the low-level hydrogen sulfide concentrations
that normally occur in communities near landfills. As mentioned
previously, hydrogen sulfide concentrations in the air around
a landfill are usually less than 15 ppb (CTDPH 1997). See the
box below for more detailed information
about the health effects associated with exposures to various
concentrations of hydrogen sulfide. Figure 3-2
displays the health effects of hydrogen sulfide exposure at
- Ammonia. Studies of health effects resulting
from exposure to ammonia have found that people who inhale 50,000
ppb of ammonia in the air for less than 1 day experience slight
and temporary irritation. Irritation, therefore, begins at concentrations
at or above the odor threshold. People exposed to 500,000 ppb
for 30 minutes increase their air intake and report soreness
of the nose and throat. Ammonia can be fatal when a person is
exposed to 5,000,000 ppb for under 30 minutes. This concentration
is equivalent to an atmosphere containing 0.5% ammonia. A study
of chronic ammonia exposure found that people exposed to ammonia
at a concentration of 100,000 ppb in air for more than 6 weeks
experienced eye, nose, and throat irritation (ATSDR 1990). Concentrations
of ammonia in the ambient air near a landfill are expected to
be well below the levels at which any adverse health effects
are expected to occur.
- NMOCs. The health effects of other landfill gas constituents, such as NMOCs, need to be considered on a chemical-by-chemical basis. It is also important to consider their possible cumulative effects. In general, levels of individual landfill gases in ambient air are not likely to reach harmful levels. In other words, low levels of landfill gases are unlikely to cause obvious, immediate health effects. However, the potential health effects from long-term exposures to low levels of landfill gases released to ambient air are not easy to evaluate, largely because exposure data are often lacking.
Researchers have studied both animal and human subjects (including asthma sufferers) to learn about possible health effects resulting from exposure to varying concentrations of hydrogen sulfide. Bear in mind that concentrations of hydrogen sulfide in the ambient air near a landfill are expected to be well below the levels at which any long-term illnesses expected to occur; however, acute symptoms may occur as a result of the strong odor associated with hydrogen sulfide.
Experimental animal studies have generally found that hydrogen sulfide does not cause harm at levels as high as 5,000 ppb. Studies of pregnant mice with daily exposures of up to 20,000 ppb concluded that hydrogen sulfide does not alter fetal development. One study showed no effects at levels up to 150,000 ppb (ATSDR 1999a).
In two laboratory studies of human subjects, healthy persons experienced no significant health effects when exposed to hydrogen sulfide concentrations of up to 5,000 ppb. Some blood chemistry levels were affected, but the ability of the subjects to function was not hampered (Bhambhani et al. 1996, 1997).
Other studies examined human exposure at workplaces such as animal-processing or sewage treatment plants, where concentrations of hydrogen sulfide are much higher than those expected to be encountered in communities. These studies found that eye irritation is the first symptom reported, and irritation usually does not occur until hydrogen sulfide concentrations reach 5,000 to 10,000 ppb. At levels from 10,000 to 50,000 ppb, people have reported severe eye and respiratory irritations. Symptoms usually end when the concentrations decrease or exposures stop. At very high concentrations (above 500,000 ppb), hydrogen sulfide can be fatal. These high concentrations are likely to be found only in enclosed spaces with limited ventilation, such as storage tanks or silos (ATSDR 1999a).
Studies of asthma sufferers have shown no significant health effects at concentrations as high as 2,000 ppb. Some asthmatics have shown mild bronchial restriction at 2,000 ppb. Epidemiologic studies of asthma sufferers and workers in pulp mills (another common source of hydrogen sulfide) did not identify any significant health effects from exposure to hydrogen sulfide concentrations in the air (Jäppinen et al. 1990; Rossi et al. 1993).
Many exposures to landfill gas involve chemicals at low or trace levels, as well as mixtures of chemicals. Most studies that look at health effects from chemical exposures consider much higher chemical exposures levels than those associated with landfills. Only a small number of studies have looked at low-level, multi-chemical exposures. The handful of studies looking at possible long-term adverse health effects (e.g., cancer) associated with low-level and multi-chemical exposures associated with living near landfills have been largely inconclusive. Appendix C contains summaries of five such studies. Although each study found some increase in reproductive effects or cancer incidence, overall, the data were inconclusive. In each study, the researchers noted the lack of data both about specific landfill gas emissions and about the effects of confounding factors such as lifestyle choices that may affect the health of individuals exposed to landfill gas emissions. Investigators noted that a study of a single landfill and the surrounding community is unlikely to answer the question of whether landfill gases are adversely affecting the health of community members. In all cases, the investigators cited the need for additional studies.
How can environmental health professionals assess whether landfill gas emissions may be posing a health threat?
If landfill gas or ambient air monitoring data are available for the landfill, a first step in assessing potential health hazards would be to compare detected concentrations against available screening values. In doing so, it is important to consider exposure point concentrations (i.e., What are the concentrations in the air that people are breathing?).Unfortunately, ambient air data are rarely available (especially in areas neighboring a landfill).
Landfill gas data can help rule out problems (i.e., if landfill gas readings are below screening levels, concentrations in ambient air will be even lower). Landfill gas data can also be used in mathematical models that predict concentrations in ambient air. But without measured ambient air data, it is difficult to determine the extent to which elevated landfill gas readings might be affecting ambient air. (See Chapter Four for information about how landfill gas is monitored, how to evaluate the adequacy and representativeness of data, and how models can be used to predict ambient air concentrations.)
Both ATSDR and EPA have developed screening values to evaluate air exposures. These screening values have been conservatively derived from experimental (animal) and human studies. ATSDR's minimal risk levels (MRLs) can be found on the web at http://www.atsdr.cdc.gov/mrls/index.html. EPA's risk-based concentrations (RBCs) can be found at http://www.epa.gov/reg3hwmd/risk/riskmenu.htm. EPA's human health medium-specific screening values can be found at http://www.epa.gov/earth1r6/6pd/rcra_c/pd-n/screen.htm. In addition, many states have developed health-based air standards or guidelines.
These screening values consider sensitive effects and often apply uncertainty factors to account for the lack of knowledge about toxic effects and human variability.1 Screening values can therefore be much lower than levels at which adverse health effects have actually been observed in studies. Depending on the chemical, screening values may be available to assess both short-term (acute) and long-term (chronic) effects and exposures.
If chemicals detected in landfill gas or air surrounding the landfill are below chemical-specific screening values, adverse health effects are unlikely. If chemicals are detected above screening values, it does not necessarily indicate that adverse health effects would be expected in a community, but that further evaluation is necessary. Site-specific exposures need to be closely examined and chemical-specific information should be researched to assist the community with understanding what is known about these possible exposures.
Information about chemical-specific toxicity is available through a variety of sources. ATSDR's toxicological profiles, for example, provide a summary of health studies for a chemical and provide an overall perspective of the chemical's toxicity. ATSDR ToxFAQs briefly describe key chemical-specific health issues (http://www.atsdr.cdc.gov/toxfaq.html.) Other on-line sources of toxicologic information include the National Library of Medicine's Medline (http://www.nlm.nih.gov/hinfo.htm) or TOXNET (http://toxnet.nlm.nih.gov/) and EPA's Integrated Risk Information System (IRIS) (http://www.epa.gov/iris/).
If monitoring data indicate that elevated concentrations of landfill gas are entering a community and that the landfill gases could plausibly be linked with adverse health effects, immediate public actions should be taken to prevent or reduce human exposure, and a site-specific health study could be considered.
Landfill fires may or may not be directly caused by landfill gas; however, because of the potential health and safety issues that they pose (e.g., gases released during the fire), this primer provides information about landfill fires.
If conditions are right, landfill fires can burn underground. Underground fires are extremely difficult to combat and can burn for days or even weeks. The heat from the fire can cause chemicals to volatilize or break down and enter the environment. Consumer products in a landfill are the most likely source of chemical releases; these products may include pesticides, paints, solvents, cleaners, or chemical additives. These chemicals may be released in smoke from the fire.
Currently, no scientific publications are available that address health effects from inhaling smoke produced during landfill fires. In order to answer concerns about potential health effects of smoke, a health professional can evaluate potential health effects posed by the particulate matter and individual chemicals emitted during the fire. It is important to note, however, that although a single chemical in the smoke may not be present in concentrations that are high enough to cause health effects, the effects of a combination of chemicals may produce unknown health reactions. Ambient air sampling and monitoring data from the community can most accurately identify the contaminants being released during the fire.
Public health and environmental professionals may be called on to develop responses for preventing or reducing community exposures to landfill fire smoke and emissions. Guidance on landfill fires developed by ATSDR describes possible responses (a copy of this guidance is provided in Appendix B). The guidance describes action levels that can be developed, using monitoring data along with assumptions about the fire's duration. The action levels are then used as triggers for measures to protect public health. For example, at certain particulate matter or chemical concentrations, the guidance recommends that people remain indoors and close windows and doors. The guidance also states that if the concentration increases, it may be appropriate to evacuate people within a certain radius of the landfill.
- The American Lung Association. http://www.lungusa.org/asthma/index.html.
- ATSDR. http://www.atsdr.cdc.gov/.
- ATSDR Exposure Investigation: Hydrogen Sulfide in Ambient Air, Dakota City/South Sioux City, Nebraska: http://www.atsdr.cdc.gov/HAC/PHA/dakcity/dak_toc.html.
- EPA. Climate Change, Methane and Other Greenhouse Gases.
- EPA. Integrated Risk Information System (IRIS). http://www.epa.gov/iris/.
- National Library of Medicine. MEDLINE/PubMed. http://www.ncbi.nlm.nih.gov/sites/entrez.
- National Library of Medicine. TOXNET (Toxicology Data Network). http://toxnet.nlm.nih.gov/.
- AIHA. 1989. American Industrial Hygiene Association. Odor Thresholds for Chemicals with Established Occupational Health Standards. 1989.
- Atlanta Journal-Constitution. 1999. Mysterious gas blast closes park. February 9, 1999.
- ATSDR. 1990. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Ammonia. 1990. Atlanta: U.S. Department of Health and Human Services.
- ATSDR. 1999a. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Hydrogen Sulfide. July 1999. Atlanta: U.S. Department of Health and Human Services.
- ATSDR. 1999b. Agency for Toxic Substances and Disease Registry. A Panel Study of Acute Respiratory Outcomes, Staten Island, New York. Draft Final Report for Public Comment. Atlanta: U.S. Department of Health and Human Services. August 20, 1999.
- Bhambhani Y, Burnham R, Snydmiller G, and MacLean I. 1997. Effects of 10 ppm hydrogen sulfide inhalation in exercising men and women. J. of Occup. and Environ. Med. 39: 122-9.
- Bhambhani Y, et al. 1996. Effects of 10 ppm hydrogen sulfide inhalation on pulmonary functions in healthy men and women. J. of Occup. and Environ. Med. 38: 1012-7.
- Charlotte Observer. 1994. Woman severely burned playing soccer. November 7, 1994.
- CTDPH. 1997. Connecticut Department of Health. Fact Sheets: Municipal Solid Waste Landfill Gases and Reproductive Health and the Danbury Landfill. January, 1997.
- EPA. 1991. U.S. Environmental Protection Agency. Air emissions from municipal solid waste landfills: background information for proposed standards and guidelines. EPA-450/3-90/011a. March 1991
- Jacobs T, 1999. Olfaction. http://www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/olfact1.html.. Downloaded December 28, 2001. Last update January 2001.
- Jäppinen P, Vilkka V, Marttila O, and Haahtela T. 1990. Exposure to hydrogen sulfide and respiratory function. British J. of Ind. Med. 47: 824-828.
- NJDHSS. n.d.. New Jersey Department of Health and Senior Services, Division of Epidemology, Environmetal and Occupational Health. Right to Know Program. http://www.state.nj.us/health/eoh/rtkweb/.
- NTP. n.d. National Toxicology Program. Chemical Health and Safety Data. http://ntp-server.niehs.nih.gov/Main_Pages/Chem-HS.html.
- OSHA. n.d.a. Occupational Safety and Health Administration. Preamble - Respiratory Protection, VII. Summary and Explanation.
- OSHA. n.d.b. Occupational Safety and Health Administration.
Asphyxiating Atmospheres, Section 12: Confined Space Hazards.
Rossi OV, et al. 1993. Association of severe asthma attacks
with weather, pollen, and air pollutants. Thorax. Mar; 48(3):
- USACE. 1984. U.S. Army Corps of Engineers. Landfill gas control at military installations, Prepared by R.A. Shafer. Publication Number CERL-TR-N-173. January 1984.
- Zero Waste America. n.d. Landfill Emissions. http://zerowasteamerica.org.
1 ATSDR's MRLs look at noncancer effects. EPA's RBCs and some state guidelines may also consider possible cancer effects.