HEALTH CONSULTATION
WISCONSIN AVENUE SCHOOL CHEMICAL VAPORS
MILWAUKEE, MILWAUKEE COUNTY, WISCONSIN
This consultation provides an evaluation of petroleum vapors entering the indoor air of the Wisconsin Avenue Elementary School in Milwaukee. This school is located at 2708 West Wisconsin Avenue in the City of Milwaukee. School district staff identified chemical odors at the school. Followup investigations conducted by district staff and contractors for the adjacent business identified petroleum contamination entering the basement foundation through vapor intrusion. The results of the investigations based on current conditions did not identify a health hazard. However, some mitigation work is clearly needed to prevent long-term exposures of health concern. The contaminant source should be better characterized and removed. Information about current conditions and planned cleanup activities should be discussed with staff at the school.
After a recent rainfall event, Milwaukee Public Schools (MPS) building management staff were contacted about gasoline odors coming from a small utility room in the basement of the Wisconsin Avenue School. Gasoline odors had not been noticed previously in this building. A former gas station on an adjacent property has been identified as the likely source of the gasoline vapors/odors entering the building. Soil contamination possibly related to existing utilities outside the building foundation seems to be the source of the most significant impact to indoor air.
MPS staff informed the Wisconsin Bureau of Environmental Health (BEH) that a high photo ionization detector (PID) reading of 50 instrument units was recorded in the small utility room, near the opening in the wall where odors were strongest. This reading is roughly 50 parts per million for total petroleum related VOCs. That level is roughly 300 times below the lower explosive limit for gasoline, making a fire and explosion hazard unlikely.
The odors outside the utility room were no longer evident after a few days. Inside the utility room the odors lasted only a day or two longer and, since February 23, 2001, are no longer noticeable. MPS staff also indicated that when the building ventilation system is operating there appears to be a positive air pressure created inside the building effectively preventing the vapors from entering. Because the building ventilation system has recently been "balanced", a positive pressure would be expected.
SUMMA Canister Samples
MPS staff have provided BEH with the results of four air samples collected
on February 16th and 17th, 2001. These samples were collected
in SUMMA canisters and analyzed for VOCs using EPA method TO-14. A summary of
these results is included in Table 1. The first sample was collected on Friday
(2/16) afternoon from the utility room when the ventilation system was shut
down and odors were present. The results of that sample show the highest chemical
concentrations by far. The remaining samples were taken the following day from
classrooms and hallways in parts of the building used daily by children and
staff. Prior to collecting these samples the ventilation system was operated
overnight and allowed to run during sampling. After collecting these samples
(about noon) the ventilation system was turned off. The VOCs detected are all
representative of gasoline contamination.
Table 1. SUMMA Canister Analysis
Wisconsin Avenue School - February 16-17, 2001
Results in Parts Per Billion by Volume (ppbv) unless otherwise indicated
| Parameter | Basement Utility Room 2/16/01 | Basement Class/Hall 2/17/01 | 1st Floor Room 13 (0205) 2/17/01 | First Floor Room 13 (0005) 2/17/01 | Comparison Value |
| Benzene | 34 | 3.0 | 0.8 J | 0.9 J | 0.03 CREG |
| Toluene | 790 D | 7.0 | 3.0 | 3.0 | 1,000 EMEG |
| Ethyl benzene | 350 D | 1.0 | 0.9 J | 0.9 J | 300 EMEG |
| Xylenes (total) | 1570 D | 6.0 | 4.0 | 4.0 J | 100 EMEG |
| Pentane | 14 | 37 | 9.0 | 10 | NA |
| Methyl t-butyl ether | 1 J | ND | ND | ND | 700 EMEG |
| Hexane | 19 | 5.0 | 2.0 | 2.0 | 60 EMEG |
| Octane | 170 D | 0.6 J | ND | ND | NA |
| Total C4-C10 Hydrocarbons | 6.0 ppmv J | <3.0 ppmv | ND | ND | NA |
| Methane | 13 ppmv | 6.8 ppmv J | 5.4 ppm J | 6.5 J | NA |
D - Sample diluted at the lab
J - Compound detected lab's limit of quantitation - concentration estimated
ND - Compound Not Detected
ppmv - Parts Per Million by Volume
CREG - Cancer Risk Evaluation Guide.
Levels above this threshold do not necessarily represent a health concern. However,
exposures to lower concentrations are very unlikely to pose an increased cancer
risk. This level is base on a lifetime of continuous exposure which is not reflective
of exposures in this situation.
EMEG - Environmental Media Evaluation
Guide. Exposure to concentrations below this threshold are very unlikely to
cause non cancer health effects. Based on ATSDR Minimal Risk Level.
NA - Comparison Value not available for this compound.
Charcoal Tube Samples
On Sunday February 18th, with the ventilation system still turned
off, thirteen charcoal tube samples were collected from various locations in
the building. Four samples were collected in various parts of the building's
basement. These samples were analyzed for the primary indicators of gasoline
vapor contamination (benzene, ethylbenzene, toluene, xylenes and total VOCs
as gasoline). As with previous observations and sampling, the sample from the
utility room contained the highest concentrations of gasoline related chemicals.
The samples from the first, second, and third floors contained generally lower
levels than those from the basement. Two samples collected from a boiler room
located in a sub-basement did not show significant impacts. Two outdoor samples
were collected at the same time. A sample from near the air intake vent on the
roof and one from ground level outside the principal's office contained low
and no detectable gasoline related VOCs respectively.(1)
Table 2 contains a summary of the results from the charcoal tube samples.
Table 2. Charcoal Tube Sample Results
Wisconsin Avenue School - February 18, 2001
Results in Parts Per Billion by Volume (ppbv)
| Parameter | Basement | Basement Closet | Basement | Basement | 1st Floor | 1st Floor | 1st Floor | Boiler Room | Boiler Room | 2nd Floor | 3rd Floor | Roof Air Intake | Principal's | Comparison Value |
| Benzene | 5.0 | 4.0J | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.03 CREG |
| Toluene | 19 | 7.0 | 7.0 | 3.0J | 3.0J | ND | ND | ND | ND | ND | 3.0J | ND | ND | 1000 EMEG |
| Ethyl benzene | 9.0 | 3.0J | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 300 EMEG |
| Xylenes (total) | 54 | 12 | 3.0 | ND | 2.0J | ND | ND | ND | ND | ND | 2.0J | ND | ND | 100 EMEG |
| Total VOCs as Gasoline* | 1200 | 400 | 244 | 31 | 72 | 16 | ND | 14J | 16 | 32 | 42 | 4.0J | ND | NA |
Because the charcoal tube method involves a very different sampling and analysis process than that of the SUMMA canister, the results from the two sampling events should only be compared qualitatively. The limit of detection for benzene in the charcoal tubes (2.0 ppbv) is also not as sensitive as that of the SUMMA canisters.
Gasoline is a complex mixture of thousands of chemicals. MPS staff noted that odors have only been faint and infrequent in areas commonly occupied by staff. These areas were not used after the odors were noted. Because the odor thresholds for toluene and xylenes are so low, faint and infrequent odors are an indication of exposure to relatively low levels of gasoline vapors. Short-term exposures during the brief period (<two weeks) when odors were noted are below levels of health concern.
Because it is a known human carcinogen, benzene is the primary gasoline related contaminant of concern for evaluating long-term exposures. Long term exposure to benzene in gasoline vapor below the odor threshold, can contribute to an increase in overall cancer risk (2). For less than several years of exposure, at the levels measured shortly after the problem was found, the risks would be quite low. However, even these low risks are unnecessary and should be avoided. The three samples collected in and near classroom areas found benzene levels at 0.8, 0.9, and 3.0 ppbv.(3) The highest of those concentrations was detected in a sample taken in a basement-level classroom area closer to the utility room. The vapor concentrations in the utility room were above the odor threshold when that first sample was collected on Friday. The level of benzene in that sample was 34 parts per billion by volume (ppbv), though it is not representative of likely exposure concentrations.(4)
There are no chemical specific indoor air quality standards for schools. Most sampling and analytical methods currently available cannot consistently detect benzene below levels of possible health concern. For this reason, BEH recommends that benzene levels in residential indoor air be below levels of detection using the lowest detection limits practically achievable (generally 0.1 to 1.0 ppbv). (5) The period of exposure is considerably less in a school than in a residence, but a similar recommendation is appropriate because children are among the most sensitive individuals to chemical exposures. The Agency for Toxic Substances and Disease Registry (ATSDR) has an acute minimal risk level (MRL) of 50 ppbv for benzene. Short-term exposures (less than two weeks) to this level and below are not expected to cause health effects. The cancer risk based comparison value of 0.03 ppbv was developed based on lifetime residential exposures assumptions, and significantly over states the risk to a school employee or student.
Unfortunately, in Milwaukee and every other community in the country, benzene is often detectable in ambient air. Past studies of urban air quality in Wisconsin (including Milwaukee) found average benzene levels to be between 0.28 ppbv and 0.38 ppbv. (6) Sampling conducted in July of 2000 at another Milwaukee public school found benzene levels between 0.28 and 1.2 ppbv in indoor air, while outdoor levels were between 0.8 and 1.4 ppbv.(7) A sample of outdoor air quality at the Wisconsin Avenue School was not collected during the indoor air sample collection. If additional sampling will be conducted in the future, a concurrent outdoor sample would be useful for this reason.
Wind speed, temperature, barometric pressure, rainfall and other weather factors can have a dramatic effect on indoor air quality related to vapor intrusion into buildings. Other factors such as opening doors, and heating/cooling and ventilation system operation are also variable and have a significant effect. For this reason, analytical sample results of indoor air quality cannot be used as quantitatively as we would like. Qualitative indicators such as odor, are often more useful to us in evaluating air quality related to contaminants such as gasoline with low odor thresholds.
The odors related to gasoline vapors are very important as an indicator of the degree of the problem. Therefore, it is very important that air fresheners and other cover scents not be used. These chemicals merely mask existing odors and provide additional unnecessary chemical exposures. Similarly, projects (other than standard school work and art projects) that involve painting or wood finishing should be postponed (if practical) until we are confident that an interim solution is in place. It currently appears that the vapor intrusion is caused by rainwater infiltration influencing the migration of an existing contamination problem. This factor would make the problem more sporadic rather than continuous. Special effort should be made to check for odors in the utility room during and immediately after rainfall or other significant weather events.
Because operating the ventilation system may reduce and possibly prevent the intrusion of gasoline vapors, this system can be an important part of the short-term solution to the problem. A simple smoke test while the system is operating and while it is not can tell you if it is having the desired impact. This type of test should be done at a few different locations of the basement foundation in case the pressure isn't evenly balanced within the building. Other options to consider would involve creating a negative pressure on the outside of the basement foundation. This would also effectively prevent vapor intrusion similar to a radon mitigation system. Ultimately the source of contamination outside the building should be cleaned up to provide the most complete and effective results.
Methane
The SUMMA canister results also identified low but measurable levels of
methane. Methane is not generally related to gasoline related contamination.
In indoor air it is most commonly related to sewer gas. At the trace concentrations
that were detected a significant problem is not expected. BEH still recommends
periodically checking to see that floor drain traps are full of water and wastewater
pipes are properly vented away from the air intakes for the ventilation system.
This case involves the air quality of an elementary school. Children can be more sensitive to the effects of chemical exposures than adults. At concentrations in the range of the odor threshold and above for petroleum contaminants, children with preexisting respiratory problems may be the most sensitive to the short term irritation effects of exposure. Because children may attend this school over several years, chronic health effects could also be of concern if vapor intrusion recurs and is not addressed effectively and permanently.
The cooperative participation of all parties in this case indicates that these recommendations can and will be followed and that all health issues will be effectively addressed.
MPS has provided instructions to staff in the school on how to respond if an indication of vapor intrusion comes up in the future.
DHFS will continue to work with MPS staff and the contractor conducting the investigation and cleanup work to ensure that health questions are addressed as they arise. DHFS has provided this consultation to staff at the school and MPS will contact DHFS if any health concerns are raised in the future.
Chuck Warzecha
Wisconsin Department of Health and Family Services
(608) 267-3732
This Wisconsin Avenue School Chemical Vapors public health consultation was prepared by the Wisconsin Department of Health and Family Services under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the public health consultation was begun.
Roberta Erlwein
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Lisa C. Hayes
for Chief, SPS, SSAB, DHAC, ATSDR
