Building ductwork gets the lead out
The General Administration Building is a five-story structure with a basement. The building houses approximately 1,500 state employees and contractors. It is occupied by a variety of state agencies, with the largest tenant being the State of Washington General Administration Department.
The other building tenants include the State of Washington Department of Revenue, the Washington State Auditors Office, the Washington State Treasurer’s Office, the State of Washington Highway Patrol, and the State of Washington Department of Licensing.
A general study of the indoor air quality problems was conducted in December 1997 by the Radix Ortega Group, Inc., Seattle, under subcontract to Washington Engineering, Inc., Bremerton, Wash. This survey included an analysis of the lead content in a dust sample collected from a ventilation diffuser.
The lead concentration in the bulk sample was 790 ppm. The relatively low concentration of lead in the sample (0.079%) did not indicate a potential airborne hazard to occupants.
However, the report became public information, and a person on the fourth floor saw the report and raised the issue of the lead that was noted.
In particular, the person wanted to know what procedures were being used for the cleanup of the building.
Further samplingFurther sampling was performed on June 12, 1998, by the Radix Ortega Group for Washington Engineering, to address these issues.
The following sampling was performed:
- Collection of air samples from four locations within the building and from one location outside of the building at the outside air intake;
- Collection of two water samples from drinking fountains; and
- Collection of six wipe samples from desks, shelves (building interior), and a cooling coil from the building’s hvac system.
Investigation methodsAir samples: Lead air sampling locations were distributed throughout the building. Sampling pumps were run throughout the day to obtain representative samples of airborne lead.
Air samples were obtained by drawing a known amount of air through a 37-mm, mixed cellulose-ester filter cassette. The cassette was attached via Tygon tubing to a SKC-brand air sampling pump. A total of five SKC pumps were used, and placed about 4 to 5 ft above the floor, to model worker breathing zone exposures.
The sample pump flow rates were adjusted using a precision rotometer. The rotometer is an instrument that measures sustained vacuum flow rates. The measured rate for each individual pump was calibrated against a National Institute for Occupational Safety and Health (NIOSH) primary standard.
Drinking water samples: Water samples were collected from two drinking fountains located on the fourth floor of the building. The fountains on this floor are located at the end of the risers. Therefore, the water supply on the fourth floor has the longest residence time within the plumbing system. If lead were present in the system, the fourth floor would be expected to have the highest concentration.
The water samples were drawn into laboratory provided, precleaned, 1-l glass sampling containers.
Wipe samples: Five wipe samples were collected from various desks and shelves located in occupied areas of the fourth floor. The fourth floor supply diffusers had the highest amounts of dust buildup. The reason is probably due to the close proximity to the recirculating fan units and fresh air intakes located on the penthouse.
An additional wipe sample was collected from the cooling coils located in fan unit S-1 in the building penthouse. Wipe samples were collected using sterile gauze pads wetted with deionized water.
An area of 1 sq ft was sampled from the desks and shelves, while an area of 16 sq in. was sampled from the fancoil. The wipe samples were collected by wiping the gauze pad in several directions on the sampled surface, and then placing the sample in a pre-labeled plastic bag.
Laboratory analysisAll samples were hand delivered to Prezant Associates, Inc., Seattle, following collection, and chain of custody was documented using sample tracking forms. Prezant Associates is an American Industrial Hygiene Association accredited analytical laboratory for bulk samples. The laboratory is also accredited by the Washington Department of Health for drinking water analysis.
The following analytical protocols were utilized to measure lead in various media:
- Â Air filter samples were analyzed according to NIOSH test method 7300.
- Â Wipe and drinking water samples were analyzed according to EPA test method 6010.
FindingsNo lead was detected in any of the air samples. The NIOSH test method 7300 detection limit is less than 0.016 mg/cu m. This detection limit is well below the OSHA permissible exposure limit of 0.050 mg/cu m.
No lead was detected in any of the water samples. The EPA test method 6010 detection limit is 10 micrograms per liter. The Safe Drinking Water Act requires that lead concentrations be maintained below 15 micrograms per liter.
No lead was detected in any wipe samples collected from the office areas. However, lead was detected in the wipe sample from the building’s fan coil. Lead in this sample was measured at a concentration of 0.711 mg/sq ft. No specific standards exist for the presence of lead on the surfaces of ventilation systems.
The Department of Housing and Urban Development requires abatement of federally owned housing if lead levels on window sills exceed 0.500 mg/sq ft (24 CFR 37.12). These cleanup criteria are designed to protect young children who tend to ingest dust and dirt.
However, the fan coil units are not accessible to building occupants. The potential for the lead becoming airborne is extremely low, as the residues containing this lead are oily and tightly adhere to the coil. This conclusion is supported by the air and wipe sample results from the occupied areas of the building, from which no lead was detected in these areas.
DiscussionThe General Administration Building is an old facility, built in 1954. Lead was used in gasoline as an anti-knock additive from the 1930s through the 1980s. The ductwork in the building had never been cleaned since it was built, which is not uncommon.
Even though the building’s fresh air intake was on the roof, there was sufficient lead in the air of downtown Olympia to contaminate the surfaces of the ductwork and the internal components of the hvac system.
The contamination consists of oily residues from diesel smoke, as well as lead bromide and lead chloride, as bromine- and chlorine-containing compounds were put in gasoline to allow lead to be scavenged from gasoline engines.
A duct and coil cleaning of the internal surfaces of the hvac system was completed in February 1999. Completion of this work has removed lead as a contaminant from the building. As lead is banned from gasoline, no further contamination of the building is expected in the future.
Air dust hazard evaluationThe potential for an airborne dust hazard was also evaluated using a simple mathematical model. The dust from the ventilation diffuser that contained lead residue as measured during the December 1997 lead survey consisted of a slightly friable, sooty film, indicating that the residue would not be easily dislodged into the air within the room.
A worst-case analysis was conducted which assumed that the lead concentration in the diffuser residue was representative of the lead level in airborne dust within the building’s office environment. The measured level of lead detected in the diffuser residue was 0.079%. A high total dust concentration for an office environment is 0.50 mg/cu m of air.
The background particulate concentration in the Puget Sound region is typically less than 0.05 mg/cu m of air. Therefore, 0.079% (lead fraction of dust) times 0.50 mg/cu m of air (total airborne dust) equals 0.000395 mg/cu m of air. Thus, the estimated worst case of airborne lead is less than l% of the permissible exposure limit of 0.05 mg/cu m of air.