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(a/k/a NICOR)


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) haveworked together to respond to the problem of elemental mercury contamination in residential homesin 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) ofliquid mercury in a small cup. The purpose of the regulator was to allow an appropriate flow of gasto the household. The mercury in the regulator acted as a seal to the relief vent in the event of apressure surge. As technology progressed, other regulators were developed that do not containmercury.

Over the past 40 years, Nicor has been replacing mercury-containing regulators located insidehomes with other regulators when they moved the meters outside. Some homes still have metersinside with mercury-containing regulators. Elemental mercury was discovered in the basements ofsome homes where Nicor or their subcontractors were replacing older gas meters. Mercury frominside 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 wherea mercury spill occurred at the home during the moving of their older gas meter and regulator by aNicor contractor. IDPH contacted Nicor and found that they were investigating this spill and threeothers in neighboring homes. IDPH and ATSDR also contacted USEPA. Subsequent investigationfound that for the past several months a Nicor subcontractor, Henkels and McCoy, Inc. (HMI), hadbeen moving gas meters with mercury-containing regulators from residential basements to theoutside of the homes in several Chicago suburbs.

During the removal of the regulators, mercury was spilled in different ways. The contractor mightremove the container containing the mercury from the regulator and leave it on the basement floorafter 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, anoverspill 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, butconfirmation air sampling procedures and cleanup goals were inadequate. USEPA instructed Nicoron the proper confirmation procedures and asked Nicor to generate and adopt a formal air samplingplan to be reviewed and approved by a multi-agency task force. The task force consisted ofrepresentatives from IDPH, ATSDR, USEPA, the Illinois Attorney General, the Cook CountyHealth Department, the Chicago Department of the Environment, the Illinois CommerceCommission, 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 investigationand cleanup of potentially contaminated homes were required. On August 1, 2000, Nicor and HMIidentified other homes in the Chicago suburban area that could have been contaminated. Someresidents of the affected homes in the Lombard area were also relocated. Some of these homes mayhave been contaminated by neighbors and friends unknowingly tracking mercury from two homeswhere the spills took place.

On August 3, 2000, Nicor compiled a list of about eighty-five homes where HMI had performed amercury regulator change within the last year. This expanded the area potentially affected to nineother suburban communities. Nicor later determined that the actual number of homes where thesubcontractor 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 haverecently removed a regulator. Some customers calling into the hotline were requesting that Nicor testtheir homes. On August 25, 2000, Nicor tested a home where a Nicor technician replaced a mercuryregulator in 1989. Elemental mercury was found in the basement near the location of the formermeter. Nicor then decided to screen all homes where either subcontractors or Nicor employees mayhave removed a mercury regulator in the past. On August 26, 2000, Nicor announced that morethan 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 andeffectively. The task force agreed that those homes where a mercury regulator was most recentlyremoved (within the last five years) or homes of young children or pregnant women would bescreened 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 thatNicor had made proper medical testing and monitoring available. IDPH also established a hotline totake health-related calls associated with mercury exposure. To date, IDPH has received more than4,000 calls on the hotline regarding mercury concerns. In addition, IDPH staff have presentedinformation about this public health response at ATSDR, Midwest Public Health Epidemiologists,and the Association of State and Territorial Health Officials (ASTHO) meetings. A mercuryeducational pamphlet and a fact sheet were made available on the IDPH web site and to interestedpersons.

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 samplelocation, occupant ages, and whether a pregnant woman resided in the home were used to evaluate ifthe home is safe for reoccupancy. Confirmation air samples were collected using the NationalInstitute for Occupational Safety and Health (NIOSH) method and analyzed at a certifiedlaboratory. Attachment 1 is an example of the sample protocol used during the cleanup ofcontaminated homes. During the cleanup phase, Nicor has moved some residents to nearby hotelsuntil the homes have been properly decontaminated and deemed safe for reoccupancy. To ensureaccurate screening and cleanup, IDPH and USEPA have tested for mercury vapor in more than 200homes. 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 andbusinesses with indoor gas regulators (Attachment 2). This document summarized and justified themercury vapor levels used in the Illinois response.

Nicor has visually inspected more than 200,000 homes. More than 90,000 homes have beensampled 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 ofthe contaminated homes found to date. At the current rate, we estimate that Nicor should identify allcontaminated homes by April 2001, and contractors should clean contaminated homes by June2001.

To date, IDPH has issued clearance letters (Attachment 3) to more than 800 homes where Nicor'scleanup resulted in mercury vapor levels less than 1 ug/m3. Confirmation air samples indecontaminated homes have averaged less than 0.3 ug/m3.

Other Gas Companies

After the media coverage of the residential mercury spills affecting Nicor customers, individualsserviced 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 than10,000 homes with a mercury vapor analyzer. Mercury has been found in sixteen homes. All sixteenhomes have been cleaned and IDPH has approved the cleanup.

Peoples Gas Company has visually inspected more than 30,000 homes to date. They have inspectedmore than 5,000 homes using a mercury vapor analyzer, and mercury has been found in sixteenhomes. 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 alsoexisted for the mercury to be unknowingly tracked throughout the home, as well as to otherresidences 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. Ingestionof and direct contact with elemental mercury are not significant routes of exposure. IDPH did notexpect to see acute health effects from exposure based on the amount of mercury known to be in aregulator. The clean up should prevent future chronic exposures and adverse health effects. Healtheffects associated with chronic exposure to elemental mercury vapor, which could have occurred inhomes 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 homeswith young children and pregnant women were prioritized for evaluation and clean up. Children 5years of age and younger are considered more sensitive to the effects of mercury on the nervoussystem, since the nervous system is still developing. The breathing zone of a child is lower to theground than that of an adult, and the amount of air breathed compared to body weight is also greaterfor children. During the investigation, homes with young children or pregnant women wereprioritized for testing.


Based on the information reviewed, IDPH concludes that a public health hazard existed frommercury contamination in many homes in the Chicago suburban area. Nicor and its contractors aredecontaminating these homes, thus eliminating future exposure to the residents.


  1. IDPH recommends that cleanup efforts continue until affected homes are at or less than the established clearance levels.

  2. IDPH recommends that USEPA or ATSDR continue to evaluate whether sample resultsusing low-detection mercury vapor analyzers correlate with the NIOSH sampling methodresults.

  3. As part of the multi-agency task force, IDPH recommended that USEPA proceed with itsplan to contact gas companies throughout Illinois and in other states to encourage them to investigate whether similar problems could exist elsewhere. USEPA Region 5 did this in December 2000. In addition, IDPH staff have presented information about the mercuryresponse at several meetings of public health officials.

  4. As part of the multi-agency task force, IDPH and ATSDR recommended that Illinois EPAcontinued with its investigation of the storage and disposal of removed regulators. Illinois EPA did this and found mercury contamination at gas company storage areas and disposal sites. Illinois EPA is addressing this issue.


Tiffanie Saxer
Environmental Toxicologist
Illinois Department of Public Health


  1. U.S. Environmental Protection Agency. Enforcement Action Memorandum for a TimeCritical Removal Action at the Nicor Mercury Spill Sites, Chicago Suburbs, Cook, DuPage,Kane, Lake, LaSalle, and McHenry Counties, Illinois. September 2000.

  2. Agency for Toxic Substances and Disease Registry, ATSDR Update Toxicological Profilefor Mercury, May 1994.


This Residential Mercury Spills from Gas Regulators Health Consultation was prepared by theIllinois Department of Public Health under a cooperative agreement with the federal Agency forToxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodologyand 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. EnvironmentalProtection Agency (USEPA), Ms. Louise Fabinski, Sr. Regional Representative for the Agency forToxic Substances and Disease Registry (ATSDR), Ms. Cherylyn Tribble, Sr. EnvironmentalEngineer for Nicor Gas, and Michael Fiore CIH, CSP from Hygeineering, Inc., the followingsampling protocol has been developed and agreed upon by all of the abovementioned as the desiredstrategy for collecting residential home mercury air samples. This protocol was designed to beimplemented once the on-site remediation service feels that the environment has been adequatelycleaned, and for the sole purpose of gathering valid data to be further assessed by Nicor and applicable governmental authorities.


  1. Prior to testing, the indoor environment will be heated to approximately 75 degreesF.

  2. Screen Test

  3. Upon initial entry, screen testing of the area shall be performed utilizing a Jeromemercury analyzer. If all readings are "non-detect" (below the sensitivity of theinstrument, which is 0.003 mg/m3), proceed to next step. If any measurableconcentrations are noted, sampling should not be performed and additional cleaningrecommended.

  4. Quantitative Sampling

  5. Prior to sampling period, the indoor temperature of home environment should bedetermined and documented. Temperature should be between 75 and 80 degrees Fthroughout the sampling period.

  6. Sampling shall be performed utilizing a pump and tube method. The pump should becalibrated to 0.5 liters/minute. The media utilized will be SKC media (AnasorbC300-comparable to hopcalite).

  7. One (1) field blank (opened in field and handled with samples) shall be taken foreach home sampled. In addition, two (2) unopened blanks from the same lot shall beretained and submitted with the corresponding field blank.

  8. A minimum of five (5) samples should be taken throughout the home. All children's bedrooms and play areas shall be tested.

  9. A floor map of the home shall be drawn to document the locations selected forsampling. The floor map shall include occupancy information identifying the roomssampled (i.e., children's bedrooms, playroom, etc.)

  10. The sample media shall be set at a height of between 3 to 4 feet from the groundlevel to represent a breathing zone sample.

  11. The sample time should be approximately eight (8) hours. Periodic pump flowchecks shall be performed and documented throughout the sampling period(minimum of 2).

  12. Upon completion of the sampling, samples shall be handled and submitted to anAIHA (American Industrial Hygiene Association?) accredited laboratory foranalysis utilizing proper chain of custody procedures. Sample turnaround time willbe determined, in advance, by Nicor and either be 24 hour or same day.

  13. The analytical sampling method to be utilized should be NIOSH 6009 or OSHAID140.

  14. Upon receipt of results, the contractor will prepare a final report and submit to Nicor for further review and follow-up action. The report shall consist of, at a minimum:
    1. Floor Map documenting the locations of samples taken and corresponding results, including a description of the occupancy of the rooms being tested.
    2. Sample data sheets documenting the media number, sample location, pump flow (with checks), final volume sampled, sample duration and any remarkable field notes.
    3. Sample results as submitted by laboratory corresponding to provided datasheets.
    4. Copy of this sampling protocol.


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 officialsin evaluating data collected from structures in which mercury pressure regulating devices for natural gas meters weremoved from inside to outside the structures as part of a modernization process. It does not provide detailed justificationsfor 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 specificnature of exposures. ATSDR has recognized that action levels can differ according to differing populations, exposuredurations, concentrations, and specific hazards. However, the immediacy and extent of the potential health risk associatedwith mercury contamination in the present situation require publication of this guide. Many parts of the country may beaffected by the possible exposure to mercury resulting from re-positioning of mercury-containing gas pressure regulatorsand the subsequent response efforts of gas utilities, public health and environmental officials. Moreover, the involvementof 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 providesuggested 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 promptconsideration of the need to implement a recommended response by public health and environmental officials. The varioussuggested action levels provided in this document are intended as recommendations, not as regulatory values or cleanupvalues, 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 sufficientconcentration over some specific period of time in order for mercury vapor to cause adverse health effects. The suggestedaction levels also recognize that while individual susceptibility may vary, developing fetuses and young children under sixyears old are generally at higher risk than others of incurring adverse health effects from exposure to mercury vapor. If theindoor air concentration corresponding to any suggested action level is exceeded, then a potential health risk may bepresent, and responders should evaluate the exposures at that location and consider implementing appropriate protectivemeasures 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 specificexperiences of ATSDR at other sites. Other factors considered in the development include available information onnormal background levels and analytical detection limits of various techniques for evaluating air borne contamination. Anyinformation specific to the exposures at any given location as described below should also be considered beforeimplementing a response action.

These suggested action levels are extrapolated from health guidance values (HGVs) independently developed by twofederal agencies, ATSDR and EPA. These HGVs are based on both animal studies and human epidemiology studies thatdetail 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 EffectLevel (LOAEL) of 26 ug/m3 over an average of 15 years. This workplace average exposure was adjusted from a 40 hourper week exposure to a 168 hour per week exposure (i.e., 24 hours/day, 7 days/week) and then divided by an uncertaintyfactor of 30 to account for the use of the LOAEL and the different sensitivities of individuals. In addition, EPA has usedthe same study to develop a Reference Concentration (RfC) of 0.3 ug/m3 , using different assumptions and uncertaintyfactors. 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 likelyto be without appreciable risk of adverse, non-cancer health effects (metallic mercury is not considered to be acarcinogenic 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 theInternet at

The suggested action levels in the tables below were designed for a group of structures where pressure regulators usingapproximately 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 thatmay have taken place some time ago, mercury was spilled in some instances. However, spills of mercury may not haveoccurred indoors. Therefore, the categories of exposure include (a) buildings that may have had no spills; (b) buildingsthat had spills and needed cleanup but had air mercury levels that constitute no immediate health risk; and (c) buildingsthat 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 buildingand moved outside; (2) observing the area where the gas meter had been originally for metallic mercury; (3) asking theresident if they had ever noticed metallic mercury in the vicinity of the gas meter; and, (4) evaluating the area with aJeromeā„¢ meter or the equivalent. If there is any positive indicator of mercury on the Jerome Mercury Vapor Analyzer (areal-time air monitoring instrument) that cannot be explained by interferences, then the building is placed on the list forfurther characterization. Visible mercury is not only a source of vapors but also a tracking hazard and an attractivenuisance. 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. Thiscondition may be considered as much a check on the data quality as anything else. It is rare that liquid mercury exists atconcentrations as low as would be considered safe in most exposure scenarios other than a workplace where mercury isused 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 tomercury exposure are those with developing central nervous systems, including young children and the fetuses of womenwho are pregnant. Other individuals of potential concern are those with pre-existing kidney conditions, usually atexposures to much higher concentrations than the first group. The specific exposure of these groups in any given situationshould be considered when assessing the need for any given response action. Specific concerns are mentioned in the tablesbelow. If there is any doubt, responders should consult with state or local public health officials before deciding on acourse 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 populationincludes infants, small children, and pregnant women presumed to have inhaled mercury for a period up to 24 hours perday, 7 days per week potentially for months or even years. Occupational or commercial settings include those individualsthat are primarily healthy adults exposed up to 8-10 hours per day, 40 hours per week, with transient exposures bysensitive populations (e.g., a retail establishment or schools). The concentrations provided as suggested action levels arefor comparison to the environmental data collected in affected residences and workplaces.

Suggested Action Levels for Mercury (CAS # 7439-97-6) - Residential Settings ā€
Indoor Air
Use of the Action LevelRationale for Action Level Method of
Analysis *
<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 safefor occupancy. ATSDR would prefer no one ever be chronically exposed to concentrationsabove the MRLs; however, experience has shown cleanup operations in a response toconcentrations below 1 ug/m 3 can be extremely disruptive to individual and family quality oflife. While this concentration is slightly above HGVs, this level is still 25 times lower thanthe human LOAEL on which the MRL is based. An indoor air concentration of 1 ug/m3 , asmeasured by the highest quality data (e.g., NIOSH 6009 or equivalent), is considered safeand acceptable by ATSDR, provided no visible metallic mercury is present.NIOSH 6009 orequivalent Based on HGVs above. ATSDR, 1999. EPA/IRIS
No qualitative detection on an Arizona Instrument's Jeromeā„¢ Meter. Screening level for homes that had indoor gas meters with no evidence of a spillMercury 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 instrumentsapproximates 1 order of magnitude below levels of known human health effects. As therewas 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 nodisruption of family life or costs. Real-time Air monitoring instrument (i.e., Jeromeā„¢ meter or equivalent)
10 Isolate residents from the exposureWhen adjusted from an intermediate to chronic exposures to a continuous exposurescenario (i.e., 24 hrs/day, 7days/week), this concentration approaches levels reported in theliterature to cause subtle human health effects. Applied to acute exposures with goodaccuracy by real-ti me instruments, this value allows for interventions before health effectswould be expected. Whenever possible, the mercury vapors should be prevented fromreaching living spaces rather than temporarily relocating individuals. See the buildingevaluation protocol developed for these situations in your area and Section 2.1 of ATSDR'sToxicological Profile. Real-time Air monitoring instrument (i.e., Jeromeā„¢ meter or equivalent)ATSDR, 1999.
10 Acceptable level in a modified test procedure to allow personal effects to remain in the owner's possessionFor personal effects, such as clothing, warmed in a discrete plastic container much smallerthan a typical room (e.g., a garbage bag), this concentration in the air trapped inside thecontainer is considered safe by ATSDR based on a number of factors.Real-time Airmonitoringinstrument (i.e.,Jeromeā„¢ meter orequivalent)

* - 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 maybe 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.
ā€ - 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 ā€
Indoor Air Concentration
Use of the Action LevelRationale 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 typicalof most workplaces. This concentration approximates one order of magnitude below levelsof known human health effects, provided no visible metallic mercury is present to act as anattractive nuisance or a source for more vapors. Those exposed in this instance would notexpect hazards associated with mercury as part of their normal work and may includetransient 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.ā€¢Based on the 1996 ACGIH TLV. Assumes hazards communications programs as requiredby OSHA; engineering controls as recommended by NIOSH; and medical monitoringprograms as recommended by the ILO, NIOSH, and ACGIH are in place. Thisconcentration is Ā½ the peer-reviewed 1973 NIOSH REL and 1/4 the regulatory1972 OSHAPEL. See HSDB at on the Internet. Real-time Air monitoring instrument (i.e., Jeromeā„¢ meter or equivalent)HSDB, 1999
25 Response Worker Protective Equipment Upgrade. ā€¢ 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 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., Jeromeā„¢ 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 on the Internet. Real-time Air monitoring instrument (i.e., Jeromeā„¢ 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.
ā€ - Structures where mercury pressure regulating devices for natural gas meters were moved from inside the structure to outside the structure.
ā€¢ - Women workers in these settings who are pregnant or attempting to become pregnant should consult their physicians regarding their mercury exposure.



March 1, 2001



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:
LocationResult (ug/m3)

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 haveconcluded that the data do not suggest a human health hazard due to mercury exposure for anyone living inthe home. No adverse health effects have been reported in the literature in persons exposed to levels less than1 ug/m3, regardless of age or condition. Based on this information, we believe it is safe for you to occupyyour home.

If you have any questions or require any additional information, feel free to contact us at 217-782-5830.


Ken Runkle
Environmental Toxicologist

cc: USEPA Region 5, ATSDR Region 5, Nicor Gas

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