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This consultation results from a Strike Team request from Mary Beth Murray, Washington County Health Department, Bartlesville, OK, concerning the re-occupation of an apartment previously contaminated with mercury. The original incident occurred on January 23, 2001 when St. Francis Hospital, Tulsa, Oklahoma notified the National Response Center that a 2-year old child had been diagnosed with acute mercury poisoning. The poisoning resulted from contamination of the parent's bedroom with mercury. ATSDR previously responded to this incident on July 8, 2001, and recommended additional sampling using NIOSH method 6009 (see ATSDR Record of Activity).

This request follows clean-up and resampling of the apartment and specifically requests that arecommendation be made as to whether re-habitation of the apartment is safe based upon thesampling results.


The sampling data provided to ATSDR is summarized in the table below; reported in levels ofmicrograms per cubic meter of air (g/m3). It is assumed from the data that the master bedroom,sampled in January 2001, is either bedroom 1 or 2 in later sampling.

Location Sampling dates
Jan 23, 2001
Jun 5, 2001
Sep 28, 2001
Master bedroom 185 floor/ 56 @ 1 meter    
Bedroom 1   0.37 0.44
Hallway     0.589
Living Room   0.35 BDL (0.41)
Living Room #2   0.39  
Bedroom 2   0.36 BDL (0.41)
Field Blank     .0494
BDC = below detection limits

The sampling data from September 28th shows small elevations in Hg levels in the hallway andbedroom #1. The levels exceed EPA's Reference Concentration (RfC) of 0.3 g/m3 and ATSDR'sMinimal Risk Level (MRL) of 0.2 g/m3. EPA's RfC and ATSDR's MRL are considered levelsbelow which there is not any concern of adverse health effects. However, the reference values do notdefine a level at which the agencies believe toxicity exists. September sampling levels, whileexceeding the reference concentrations are significantly below the lowest observable adverse effectlevel ( LOAEL) of 26 g/m3 for subtle neurologic effects (electrophysiologically-measured finemotor tremors during mechanical stress) from which both the RfC and MRL were derived (Fawer etal., 1983). These levels should not pose a public health hazard and re-occupation of the apartmentat these levels would be acceptable.

However, ATSDR is concerned about how representative the samples are of actual mercury levels in the apartment. Sampling methods and sample handling were found to have several deficiencies that may have lead to an under-determination of air levels.

  • Documentation of sampling conditions, methods, and analytical techniques was notprovided. As best as can be determined sampling was performed using the passivesampling device marketed by Heritage Environmental Services. This sampler isadvertised as being compliant with OSHA standards. OSHA sampling method #140 indicates passive samplers are only valid in the range of 61 - 200 g/m3mercury in air. They are not appropriate for quantifying low environmental levels ofmercury. ATSDR has previously recommended appropriate sampling methods forevaluation of indoor Hg levels in air (AROA, July 8, 2001).

  • Sampling was performed 1 -2 meters above the floor (personal communication withATSDR regional rep - Nov 23, 2001). This could greatly under estimate the levelsnear the floor, in the breathing zone of small children and infants.

  • Temperature of the apartment was not specified. Low temperatures can greatlydecrease volatilization of mercury and lead to lower air levels in samples.


  1. Do not re-occupy the apartment. Although sampling data indicate indoor levels donot pose a public health concern, confidence in the data collection methods is so lowthat ATSDR can only classify the apartment as an indeterminate health concern. The history of the apartment indicates acutely toxic levels of Hg have existed there inthe near past.

  2. Devise and implement an appropriate sampling plan. This plan should include thefollowing:

    • Apartment temperature - at least 80 degree F.
    • Samplers located 8 - 10 cm from the floor.
    • Samplers located in all rooms, including hallway and bathroom.
    • Sample with active sampling a minimum of 100 L of air for a LOC of 0.3 g/m3.
    • Sampling methodology should follow NIOSH 6009 or equivalent.
    • Sample holding time should not exceed 3 weeks if samples are keptat room temperature.
    • Document all sampling conditions, chain of custody, air sample flowrate, and analytical methods used.


John S. Wheeler, PhD, DABT
Senior Toxicologist
Consultation Section
Exposure Investigations and Consultations Branch
Division of Health Assessment and Consultation

Peter J. Kowalski, MPH, CIH
Environmental Health Scientist
Consultation Section
Exposure Investigations and Consultations Branch
Division of Health Assessment and Consultation

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