HEALTH CONSULTATION
RESIDENTIAL MERCURY SPILLS FROM
GAS REGULATORS IN ILLINOIS
(a/k/a NICOR)
MT. PROSPECT, LAKE COUNTY, ILLINOIS
BACKGROUND AND STATEMENT OF ISSUES
The Illinois Department of Public Health (IDPH), the U.S. Environmental Protection Agency (USEPA), Region 5, and the Agency for Toxic Substances and Disease Registry (ATSDR) have worked together to respond to the problem of elemental mercury contamination in residential homes in northern Illinois throughout the Nicor Gas (Nicor) and Peoples Energy service areas.
Before 1961, many homes in northern Illinois were equipped with gas meters using mercury-containing regulators. On average, these regulators contained about 135 grams (two teaspoons) of liquid mercury in a small cup. The purpose of the regulator was to allow an appropriate flow of gas to the household. The mercury in the regulator acted as a seal to the relief vent in the event of a pressure surge. As technology progressed, other regulators were developed that do not contain mercury.
Over the past 40 years, Nicor has been replacing mercury-containing regulators located inside homes with other regulators when they moved the meters outside. Some homes still have meters inside with mercury-containing regulators. Elemental mercury was discovered in the basements of some homes where Nicor or their subcontractors were replacing older gas meters. Mercury from inside the regulator attached to the meter spilled on the floors of some homes.
On July 22, 2000, IDPH and ATSDR were contacted by a resident of a home in Mt. Prospect where a mercury spill occurred at the home during the moving of their older gas meter and regulator by a Nicor contractor. IDPH contacted Nicor and found that they were investigating this spill and three others in neighboring homes. IDPH and ATSDR also contacted USEPA. Subsequent investigation found that for the past several months a Nicor subcontractor, Henkels and McCoy, Inc. (HMI), had been moving gas meters with mercury-containing regulators from residential basements to the outside of the homes in several Chicago suburbs.
During the removal of the regulators, mercury was spilled in different ways. The contractor might remove the container containing the mercury from the regulator and leave it on the basement floor after completing the work. The container was occasionally knocked over during the removal, spilling mercury onto the floor. Another way mercury was spilled was that, during the removal, an overspill container was not used to prevent spilling mercury onto the floor.
Nicor hired a cleanup contractor and industrial hygiene firm to perform decontamination activities. USEPA determined that the cleanup activities being done by the contractors were adequate, but confirmation air sampling procedures and cleanup goals were inadequate. USEPA instructed Nicor on the proper confirmation procedures and asked Nicor to generate and adopt a formal air sampling plan to be reviewed and approved by a multi-agency task force. The task force consisted of representatives from IDPH, ATSDR, USEPA, the Illinois Attorney General, the Cook County Health Department, the Chicago Department of the Environment, the Illinois Commerce Commission, the Illinois Poison Control Center, and the Illinois Environmental Protection Agency.
On July 31, 2000, the Illinois Attorney General's Office informed Nicor that further investigation and cleanup of potentially contaminated homes were required. On August 1, 2000, Nicor and HMI identified other homes in the Chicago suburban area that could have been contaminated. Some residents of the affected homes in the Lombard area were also relocated. Some of these homes may have been contaminated by neighbors and friends unknowingly tracking mercury from two homes where the spills took place.
On August 3, 2000, Nicor compiled a list of about eighty-five homes where HMI had performed a mercury regulator change within the last year. This expanded the area potentially affected to nine other suburban communities. Nicor later determined that the actual number of homes where the subcontractor might have worked within the last year was closer to 120. Of these 120 homes, approximately twenty homes were contaminated and required clean up.
Nicor established a hotline to identify homes where subcontractors other than HMI may have recently removed a regulator. Some customers calling into the hotline were requesting that Nicor test their homes. On August 25, 2000, Nicor tested a home where a Nicor technician replaced a mercury regulator in 1989. Elemental mercury was found in the basement near the location of the former meter. Nicor then decided to screen all homes where either subcontractors or Nicor employees may have removed a mercury regulator in the past. On August 26, 2000, Nicor announced that more than 200,000 homes would be inspected and screened. Nicor originally suggested a 90-day to 6-month period for this to be completed.
The task force worked with Nicor to develop a plan to inspect and screen the homes efficiently and effectively. The task force agreed that those homes where a mercury regulator was most recently removed (within the last five years) or homes of young children or pregnant women would be screened first. Homes with visible mercury present were given top priority.
Both ATSDR and IDPH have talked to hundreds of residents and their physicians to ensure that Nicor had made proper medical testing and monitoring available. IDPH also established a hotline to take health-related calls associated with mercury exposure. To date, IDPH has received more than 4,000 calls on the hotline regarding mercury concerns. In addition, IDPH staff have presented information about this public health response at ATSDR, Midwest Public Health Epidemiologists, and the Association of State and Territorial Health Officials (ASTHO) meetings. A mercury educational pamphlet and a fact sheet were made available on the IDPH web site and to interested persons.
ATSDR and IDPH established a cleanup clearance level of 1 microgram per cubic meter of air (ug/m3 ), and a relocation action level of 10 ug/m3 . At mercury vapor levels greater than 10 ug/m3, Nicor offered to relocate residents until the cleanup was complete. Variables such as sample location, occupant ages, and whether a pregnant woman resided in the home were used to evaluate if the home is safe for reoccupancy. Confirmation air samples were collected using the National Institute for Occupational Safety and Health (NIOSH) method and analyzed at a certified laboratory. Attachment 1 is an example of the sample protocol used during the cleanup of contaminated homes. During the cleanup phase, Nicor has moved some residents to nearby hotels until the homes have been properly decontaminated and deemed safe for reoccupancy. To ensure accurate screening and cleanup, IDPH and USEPA have tested for mercury vapor in more than 200 homes. In addition, a small number of randomly selected homes will be retested in 2001.
In December 2000, ATSDR released suggested action levels for indoor mercury vapor in homes and businesses with indoor gas regulators (Attachment 2). This document summarized and justified the mercury vapor levels used in the Illinois response.
Nicor has visually inspected more than 200,000 homes. More than 90,000 homes have been sampled with a mercury vapor analyzer, and mercury has been found in more than 1,000 homes. Several thousand homes remain to be inspected. IDPH has approved cleanups in about two-thirds of the contaminated homes found to date. At the current rate, we estimate that Nicor should identify all contaminated homes by April 2001, and contractors should clean contaminated homes by June 2001.
To date, IDPH has issued clearance letters (Attachment 3) to more than 800 homes where Nicor's cleanup resulted in mercury vapor levels less than 1 ug/m3. Confirmation air samples in decontaminated homes have averaged less than 0.3 ug/m3.
Other Gas Companies
After the media coverage of the residential mercury spills affecting Nicor customers, individuals serviced by other gas companies in northern Illinois were concerned that they may also be affected. Two other gas companies (North Shore Gas and Peoples Gas) began investigations similar to Nicor. Both companies followed the same protocols set for Nicor when sampling and cleaning homes.
North Shore Gas Company has visually inspected more than 30,000 homes and sampled more than 10,000 homes with a mercury vapor analyzer. Mercury has been found in sixteen homes. All sixteen homes have been cleaned and IDPH has approved the cleanup.
Peoples Gas Company has visually inspected more than 30,000 homes to date. They have inspected more than 5,000 homes using a mercury vapor analyzer, and mercury has been found in sixteen homes. All sixteen of these homes have been cleaned and IDPH has approved the cleanups.
Mercury vapor levels were elevated in homes where liquid mercury was spilled. The potential also existed for the mercury to be unknowingly tracked throughout the home, as well as to other residences and vehicles. To date, mercury contamination has been found in less than 1% of the homes inspected.
Persons are exposed to elemental mercury primarily through inhalation of mercury vapor. Ingestion of and direct contact with elemental mercury are not significant routes of exposure. IDPH did not expect to see acute health effects from exposure based on the amount of mercury known to be in a regulator. The clean up should prevent future chronic exposures and adverse health effects. Health effects associated with chronic exposure to elemental mercury vapor, which could have occurred in homes over time, include shyness, irritability, forgetfulness, insomnia, loss of appetite and muscle tremors.
IDPH recognizes that children are especially vulnerable to the effects of mercury vapor, so homes with young children and pregnant women were prioritized for evaluation and clean up. Children 5 years of age and younger are considered more sensitive to the effects of mercury on the nervous system, since the nervous system is still developing. The breathing zone of a child is lower to the ground than that of an adult, and the amount of air breathed compared to body weight is also greater for children. During the investigation, homes with young children or pregnant women were prioritized for testing.
Based on the information reviewed, IDPH concludes that a public health hazard existed from mercury contamination in many homes in the Chicago suburban area. Nicor and its contractors are decontaminating these homes, thus eliminating future exposure to the residents.
RECOMMENDATIONS AND PUBLIC HEALTH ACTION PLAN
Tiffanie Saxer
Environmental Toxicologist
Illinois Department of Public Health
This Residential Mercury Spills from Gas Regulators Health Consultation was prepared by the Illinois Department of Public Health under a cooperative agreement with the federal Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Roberta Erlwein
Technical Project Officer, SPS, SSAB, DHAC
Lisa C. Hayes
Section Chief, SPS, SSAB, DHAC, ATSDR
Sampling Protocol for Mercury Contamination within a Residential Home
Per discussions with Mr. Brad Stimple, On-Scene Coordinator for the U.S. Environmental Protection Agency (USEPA), Ms. Louise Fabinski, Sr. Regional Representative for the Agency for Toxic Substances and Disease Registry (ATSDR), Ms. Cherylyn Tribble, Sr. Environmental Engineer for Nicor Gas, and Michael Fiore CIH, CSP from Hygeineering, Inc., the following sampling protocol has been developed and agreed upon by all of the abovementioned as the desired strategy for collecting residential home mercury air samples. This protocol was designed to be implemented once the on-site remediation service feels that the environment has been adequately cleaned, and for the sole purpose of gathering valid data to be further assessed by Nicor and applicable governmental authorities.
ATSDR Suggested Action Levels for Indoor Mercury Vapors
in Homes or Businesses with Indoor Gas Regulators
Suggested Action Levels
for Indoor Mercury Vapors in Homes
or Businesses with Indoor Gas Regulators
Purpose: This document is intended solely as a quick reference guide for use by public health and environmental officials in evaluating data collected from structures in which mercury pressure regulating devices for natural gas meters were moved from inside to outside the structures as part of a modernization process. It does not provide detailed justifications for environmental sampling requirements, as health consultations or environmental sampling plans may do.
In the past, ATSDR has been reluctant to provide a list of suggested action levels such as this because of the site specific nature of exposures. ATSDR has recognized that action levels can differ according to differing populations, exposure durations, concentrations, and specific hazards. However, the immediacy and extent of the potential health risk associated with mercury contamination in the present situation require publication of this guide. Many parts of the country may be affected by the possible exposure to mercury resulting from re-positioning of mercury-containing gas pressure regulators and the subsequent response efforts of gas utilities, public health and environmental officials. Moreover, the involvement of multiple health and environmental jurisdictions creates a need for consistency in presenting health risk information. Therefore, ATSDR, at the request of a state health department and an U.S. EPA regional office, is attempting to provide suggested action levels for various response activities under different exposure scenarios.
Background: In this context, an action level is an indoor air concentration of mercury vapor, which should prompt consideration of the need to implement a recommended response by public health and environmental officials. The various suggested action levels provided in this document are intended as recommendations, not as regulatory values or cleanup values, although some may correspond to present or future values adopted by regulatory authorities.
The suggested action levels presented in this document recognize that an individual must be exposed to a sufficient concentration over some specific period of time in order for mercury vapor to cause adverse health effects. The suggested action levels also recognize that while individual susceptibility may vary, developing fetuses and young children under six years old are generally at higher risk than others of incurring adverse health effects from exposure to mercury vapor. If the indoor air concentration corresponding to any suggested action level is exceeded, then a potential health risk may be present, and responders should evaluate the exposures at that location and consider implementing appropriate protective measures to reduce or eliminate the risk.
The suggested action levels presented here are based on data available in ATSDR's Toxicological Profile for Mercury (1999) or in the Hazardous Substance Databank of the Toxicology Data Network at the National Library of Medicine. ATSDR has also made use of additional data collected by the US Environmental Protection Agency (EPA) and of specific experiences of ATSDR at other sites. Other factors considered in the development include available information on normal background levels and analytical detection limits of various techniques for evaluating air borne contamination. Any information specific to the exposures at any given location as described below should also be considered before implementing a response action.
These suggested action levels are extrapolated from health guidance values (HGVs) independently developed by two federal agencies, ATSDR and EPA. These HGVs are based on both animal studies and human epidemiology studies that detail the health effects of inhalation of mercury-contaminated air. ATSDR has developed a chronic Minimal Risk Level (MRL) of 0.2 ug/m3 that is based on a 1983 study of workers exposed to an average Lowest Observed Adverse Effect Level (LOAEL) of 26 ug/m3 over an average of 15 years. This workplace average exposure was adjusted from a 40 hour per week exposure to a 168 hour per week exposure (i.e., 24 hours/day, 7 days/week) and then divided by an uncertainty factor of 30 to account for the use of the LOAEL and the different sensitivities of individuals. In addition, EPA has used the same study to develop a Reference Concentration (RfC) of 0.3 ug/m3 , using different assumptions and uncertainty factors. ATSDR considers the RfC and the Chronic MRL to be the same value for all practical purposes. An MRL, then, is defined as an estimate of the daily exposure level to a hazardous substance (in this case, metallic mercury) that is likely to be without appreciable risk of adverse, non-cancer health effects (metallic mercury is not considered to be a carcinogenic substance) over a specific exposure route and duration of exposure. For further information, see Section 2.5, Chapter 7, and Appendix A of the ATSDR Tox Profile and the EPA's Integrated Risk Information System (IRIS) on the Internet at www.epa.gov/ngispgm3/iris/index.html.
The suggested action levels in the tables below were designed for a group of structures where pressure regulators using approximately 2 teaspoons (and perhaps more) of mercury (~10 ml or 135 g) and the accompanying gas meters were re-positioned from the interior of buildings (including homes) to the exterior. During this adjustment of regulator location that may have taken place some time ago, mercury was spilled in some instances. However, spills of mercury may not have occurred indoors. Therefore, the categories of exposure include (a) buildings that may have had no spills; (b) buildings that had spills and needed cleanup but had air mercury levels that constitute no immediate health risk; and (c) buildings that had spills resulting in indoor air concentrations sufficient to warrant isolating humans from the exposure. In general, the screening for these homes or businesses consists of: (1) confirming that a natural gas meter had been in the building and moved outside; (2) observing the area where the gas meter had been originally for metallic mercury; (3) asking the resident if they had ever noticed metallic mercury in the vicinity of the gas meter; and, (4) evaluating the area with a Jerome™ meter or the equivalent. If there is any positive indicator of mercury on the Jerome Mercury Vapor Analyzer (a real-time air monitoring instrument) that cannot be explained by interferences, then the building is placed on the list for further characterization. Visible mercury is not only a source of vapors but also a tracking hazard and an attractive nuisance. No matter what the airborne concentration is, free liquid mercury may pose a problem in the general population. Generally, a condition that no visible mercury be present is stipulated only at stages when cleanup is completed. This condition may be considered as much a check on the data quality as anything else. It is rare that liquid mercury exists at concentrations as low as would be considered safe in most exposure scenarios other than a workplace where mercury is used in the production process.
General Exposure Assessment Considerations: The primary route of entry for metallic mercury is by inhalation; ingestion and skin absorption of this form of mercury is usually not biologically significant. Sensitive populations to mercury exposure are those with developing central nervous systems, including young children and the fetuses of women who are pregnant. Other individuals of potential concern are those with pre-existing kidney conditions, usually at exposures to much higher concentrations than the first group. The specific exposure of these groups in any given situation should be considered when assessing the need for any given response action. Specific concerns are mentioned in the tables below. If there is any doubt, responders should consult with state or local public health officials before deciding on a course of action. Responders may also contact ATSDR at 404-639-0615, 24 hours a day.
Exposure Assumptions for Different Settings: For the purposes of this document, the residentially exposed population includes infants, small children, and pregnant women presumed to have inhaled mercury for a period up to 24 hours per day, 7 days per week potentially for months or even years. Occupational or commercial settings include those individuals that are primarily healthy adults exposed up to 8-10 hours per day, 40 hours per week, with transient exposures by sensitive populations (e.g., a retail establishment or schools). The concentrations provided as suggested action levels are for comparison to the environmental data collected in affected residences and workplaces.
Suggested Action Levels for Mercury (CAS # 7439-97-6) - Residential Settings †
| Indoor Air Concentration (ug/m3) |
Use of the Action Level | Rationale for Action Level | Method of Analysis * |
Reference |
| <1.0 | Level acceptable for occupancy of any structure after a spill (also called the residential occupancy level.) | A spill occurred in this building, and the risk manager needs to know if the building is safe for occupancy. ATSDR would prefer no one ever be chronically exposed to concentrations above the MRLs; however, experience has shown cleanup operations in a response to concentrations below 1 ug/m 3 can be extremely disruptive to individual and family quality of life. While this concentration is slightly above HGVs, this level is still 25 times lower than the human LOAEL on which the MRL is based. An indoor air concentration of 1 ug/m3 , as measured by the highest quality data (e.g., NIOSH 6009 or equivalent), is considered safe and acceptable by ATSDR, provided no visible metallic mercury is present. | NIOSH 6009 or equivalent | Based on HGVs above. ATSDR, 1999. EPA/IRIS |
| No qualitative detection on an Arizona Instrument's Jerome™ Meter. | Screening level for homes that had indoor gas meters with no evidence of a spill | Mercury was present in the regulator inside the home, but no evidence of a spill is found. The qualitative detection limit of the most commonly available air monitoring instruments approximates 1 order of magnitude below levels of known human health effects. As there was no spill, no visible metallic mercury should be present. Natural ventilation (e.g. , windows, HVAC air changes, etc.) should reduce any concentration even lower with no disruption of family life or costs. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) | |
| 10 | Isolate residents from the exposure | When adjusted from an intermediate to chronic exposures to a continuous exposure scenario (i.e., 24 hrs/day, 7days/week), this concentration approaches levels reported in the literature to cause subtle human health effects. Applied to acute exposures with good accuracy by real-ti me instruments, this value allows for interventions before health effects would be expected. Whenever possible, the mercury vapors should be prevented from reaching living spaces rather than temporarily relocating individuals. See the building evaluation protocol developed for these situations in your area and Section 2.1 of ATSDR's Toxicological Profile. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) | ATSDR, 1999. |
| 10 | Acceptable level in a modified test procedure to allow personal effects to remain in the owner's possession | For personal effects, such as clothing, warmed in a discrete plastic container much smaller than a typical room (e.g., a garbage bag), this concentration in the air trapped inside the container is considered safe by ATSDR based on a number of factors. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) |
* - Environmental analysis should be in accordance with the requirements specified by environmental authorities. When real-time air monitoring instruments are specified in this table, laboratory analysis may
be substituted at the discretion of the risk managers involved in the event. Operation of real-time instruments should be in accordance with manufacturer's instructions.
† - Structures where mercury pressure regulating devices for natural gas meters were moved from inside the structure to outside the structure.
Suggested Action Levels for Mercury (CAS # 7439-97-6) - Occupational and Commercial Settings †
| Indoor Air Concentration
(ug/m3) |
Use of the Action Level | Rationale for Action Level | Method of Analysis * | Reference |
| 3.0 | Re-occupancy after a spill of an occupational or commercial setting where mercury is not usually handled. | Based on residential occupancy level but adjusted for the shorter duration exposures typical of most workplaces. This concentration approximates one order of magnitude below levels of known human health effects, provided no visible metallic mercury is present to act as an attractive nuisance or a source for more vapors. Those exposed in this instance would not expect hazards associated with mercury as part of their normal work and may include transient exposures by more sensitive individuals (e.g., retail facilities). | NIOSH 6009 or equivalent | HGVs. ATSDR, 1999. EPA/IRIS |
| 25 | Occupational settings where mercury is handled.• | Based on the 1996 ACGIH TLV. Assumes hazards communications programs as required by OSHA; engineering controls as recommended by NIOSH; and medical monitoring programs as recommended by the ILO, NIOSH, and ACGIH are in place. This concentration is ˝ the peer-reviewed 1973 NIOSH REL and 1/4 the regulatory1972 OSHA PEL. See HSDB at toxnet.nlm.nih.gov/sis on the Internet. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) | HSDB, 1999 |
| 25 | Response Worker Protective Equipment Upgrade. • | Response workers subject to HAZWOPER should evaluate need to upgrade protective equipment. Based on the 1996 ACGIH TLV. Assumes hazards communications programs as required by OSHA; engineering controls as recommended by NIOSH; and medical monitoring programs as recommended by the ILO, NIOSH, AND ACGIH are in place. This concentration is half the peer-reviewed NIOSH REL and a quarter of the regulatory OSHA PEL. See HSDB at toxnet.nlm.nih.gov/sis on the Internet. For these workers, engineering controls are not typically in place, and it is not possible to control the exposure by other safety techniques. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) | 29 CFR 1910.120; 40 CFR 311; NIOSH, 1987 |
| 10,000 | IDLH. Response Workers Protective Equipment upgrade. | Response workers subject to HAZWOPER should upgrade protective equipment. See http://www.cdc.gov/niosh/idlh/ on the Internet. | Real-time Air monitoring instrument (i.e., Jerome™ meter or equivalent) | 29 CFR 1910.120; 40 CFR 311; NIOSH 1987 |
* - Environmental analysis should be in accordance with the requirements specified by environmental authorities. When real-time air monitoring instruments are specified in this table, laboratory analysis may be substituted at the discretion of the risk managers involved in the event. Operation of real-time instruments should be in accordance with manufacturer's instructions.
† - Structures where mercury pressure regulating devices for natural gas meters were moved from inside the structure to outside the structure.
• - Women workers in these settings who are pregnant or attempting to become pregnant should consult their physicians regarding their mercury exposure.
#908100001
March 1, 2001
FIRST_NAME ~ LAST_NAME ~
ADDRESS ~
CITY ~, IL ZIP ~
Dear RESIDENT:
The Illinois Department of Public Health has received the laboratory results of the air samples collected at your home on SAMPLE_DATE ~ by contractors for Nicor Gas. The results are:
|
Location |
Result (ug/m3) |
| LOCATION_1 ~ | SAMPLE_1 ~ |
| LOCATION_2 ~ | SAMPLE_2 ~ |
| LOCATION_3 ~ | SAMPLE_3 ~ |
| LOCATION_4 ~ | SAMPLE_4 ~ |
| LOCATION_5 ~ | SAMPLE_5 ~ |
| LOCATION_6 ~ | SAMPLE_6 ~ |
| LOCATION_7 ~ | SAMPLE_7 ~ |
| LOCATION_8 ~ | SAMPLE_8 ~ |
ug/m3 = micrograms of mercury per cubic meter of air
We have consulted with toxicologists at the Agency for Toxic Substances and Disease Registry and have concluded that the data do not suggest a human health hazard due to mercury exposure for anyone living in the home. No adverse health effects have been reported in the literature in persons exposed to levels less than 1 ug/m3, regardless of age or condition. Based on this information, we believe it is safe for you to occupy your home.
If you have any questions or require any additional information, feel free to contact us at 217-782-5830.
Sincerely,
Ken Runkle
Environmental Toxicologist
cc: USEPA Region 5, ATSDR Region 5, Nicor Gas
