Evaluation of Indoor 

Environmental Quality and 

Health Concerns Among 

Employees of a Public 

Elementary School

HHE Report No. 2019-0156-3382

October 2021 
Authors: Karl D. Feldmann, MS, REHS/RS, CIH

Jessica Rinsky, PhD, MPH

Laura Reynolds, MPH, BSN, RN, CPH

Desktop Publisher: Shawna Watts

Editor: Cheryl Hamilton

Industrial Hygiene Field Assistance: Josie Ehlers

Logistics: Donnie Booher, Kevin Moore

Medical Field Assistance: Sophia Chiu, Candice Johnson

Keywords: North American Industry Classification System (NAICS) Code 611110, Elementary and 

Secondary Schools; Michigan; Mold; Indoor Air Quality; IAQ; Indoor Environmental Quality; IEQ; 

Fertility; Infertility; Miscarriage; Ventilation; Heating, Ventilation, and Air-Conditioning; HVAC; 

Housekeeping; Reproductive Health; Stroke; Thyroid Disorder

Disclaimer 

The Health Hazard Evaluation Program investigates possible health hazards in the workplace under 

the authority of the Occupational Safety and Health Act of 1970 [29 USC 669a(6)]. The Health 

Hazard Evaluation Program also provides, upon request, technical assistance to federal, state, and 

local agencies to investigate occupational health hazards and to prevent occupational disease or 

injury. Regulations guiding the Program can be found in Title 42, Code of Federal Regulations, 

Part 85; Requests for Health Hazard Evaluations [42 CFR Part 85]. 

Availability of Report

Copies of this report have been sent to the employer, employees, and union at the school. The state 

and local health departments and the Occupational Safety and Health Administration Regional

Office have also received a copy. This report is not copyrighted and may be freely reproduced.

Recommended Citation

NIOSH [2021]. Evaluation of indoor environmental quality and health concerns among employees 

of a public elementary school. By Feldmann KD, Rinsky J, Reynolds L. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, Health Hazard Evaluation Report 2019-0156-3382, 

https://www.cdc.gov/niosh/hhe/reports/pdfs/2019-0156-3382.pdf. 
Table of Contents

Main Report

Introduction....................................................................................................................................................... 1

Our Approach ................................................................................................................................................... 1

Our Key Findings.............................................................................................................................................. 1

Our Recommendations.................................................................................................................................... 4

Supporting Technical Information 

Section A: Workplace Information............................................................................................................ A-1

Building...................................................................................................................................................... A-1

Employee Information ............................................................................................................................ A-1

Background ............................................................................................................................................... A-1

Section B: Methods, Results, and Discussion .......................................................................................... B-1

Methods: Review of Prior Indoor Air Quality Consultant Reports.................................................. B-1

Results: Review of Prior Indoor Air Quality Consultant Reports..................................................... B-1

Methods: On-site Building Evaluation.................................................................................................. B-3

Results: On-site Building Evaluation..................................................................................................... B-4

Methods: Employee Interviews.............................................................................................................. B-8

Results: Employee Interviews............................................................................................................... B-11

Discussion ............................................................................................................................................... B-15

Limitations............................................................................................................................................... B-19

Conclusions............................................................................................................................................. B-20

Section C: Tables.......................................................................................................................................... C-1

Section D: Epidemiology of Selected Reproductive Outcomes............................................................ D-1

Endometriosis.......................................................................................................................................... D-1

Uterine Fibroids....................................................................................................................................... D-1

Hysterectomy ........................................................................................................................................... D-2

Infertility ................................................................................................................................................... D-2

Miscarriage................................................................................................................................................ D-3

Section E: References.................................................................................................................................. E-1
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1

Introduction

Request

Employees from a public elementary school requested a confidential health hazard evaluation because 

they thought that they might be experiencing a greater burden of general and reproductive medical 

conditions than was typical. Employees were concerned that these medical conditions were related to 

something in their work environment, specifically mold or other causes of poor indoor environmental 

quality at the school.

Workplace 

At the time of our visit, the single-story, public elementary school (one of three in the county) served 

about 500 children in prekindergarten, kindergarten, and Grades 1–5. About 67 employees worked at 

the school.

To learn more about the workplace, go to Section A in the Supporting Technical Information

Our Approach

In September 2019 we visited the school. During our visit we completed the following activities:

• Visually inspected every room in the school and their associated heating, ventilation, and airconditioning (HVAC) systems.

• Evaluated every room in the school using the Dampness and Mold Assessment Tool developed 

by the National Institute for Occupational Safety and Health (NIOSH).

• Measured temperature, relative humidity, carbon monoxide, and carbon dioxide levels in eight 

occupied classrooms, the teachers’ lounge, and outside the school.

• Interviewed employees about their work and their health. Information collected included job 

tenure, job tasks, and the occurrence and timing of medical symptoms, diagnoses, and concerns.

We sent a letter summarizing our findings from the site visit and recommendations in October 2019. 

To learn more about our methods, go to Section B in the Supporting Technical Information

Our Key Findings

We found no evidence of active mold growth in the school

• We observed evidence of past roof leaks but found no visible mold, or wet/damp areas inside 

the school.
2

• We observed a leaking hose bibb near the crawlspace on the outside of the building. The 

crawlspace had some water intrusion, but no mold growth.

• We found two HVAC system condensate drains in the courtyard that did not drain into their 

respective drainpipes. 

The unit ventilators original to the building were approaching the end of their 

expected service life

• Mold was not observed on or in the unit 

ventilators we checked.

• Some classroom unit ventilators were partially or 

completely blocked by books, classroom supplies, 

or furniture (Figure 1).

• Some classrooms had exhaust fans to help move 

air though the classroom. These fans were in 

various states of operation (e.g., functioning, 

partially functioning, not functioning at all). Some

had been recently repaired.

• Carbon dioxide levels were well above outdoor 

levels in seven of the eight classrooms we 

measured. This means that the HVAC systems 

did not provide enough outdoor air to meet 

guidelines for acceptable ventilation. 

• Temperature or relative humidity levels exceeded 

professional guidelines in two of the eight 

classrooms we measured. This means that the 

HVAC systems were unable to condition the air to meet guidelines for comfort parameters.

• Some areas of the school that were not designed for prolonged occupancy (for example, storage 

rooms) were being used as classrooms. Areas with inadequate or no HVAC systems cannot 

meet professional guidelines for acceptable ventilation or comfort parameters.

Some symptoms were more common among school employees than among other 

comparable working populations

• Employees reported experiencing frequent, work-related stuffy or runny nose or sinus 

congestion and headaches. Frequent, work-related refers to symptoms that occur at least weekly 

and improve when away from work.

Figure 1. A classroom unit ventilator is 

partially blocked by furniture and 

classroom supplies. The window above it 

is open. Photo by NIOSH.
3

o The percentage of school employees reporting these symptoms was similar to what 

employees working in buildings with known indoor environmental quality complaints 

reported in previous studies.

o The percentage of school employees reporting these symptoms was elevated compared 

with what employees working in buildings without known indoor environmental quality 

complaints reported in previous studies.

o Although we cannot directly link these common and nonspecific symptoms with 

working in the school, these symptoms can be related to poor ventilation.

• Employees reported experiencing migraines or severe headaches during the previous 

three months. 

o The percentage of school employees reporting these symptoms was elevated compared 

with what was observed among U.S. teachers and paraprofessionals and with the 

U.S. female population. However, the percentage of employees reporting migraines and 

severe headaches that qualified as work-related, was lower. Work-related symptoms were 

those that improved away from work.

o No specific indoor environmental exposure has been linked with migraines and severe 

headaches. Previous studies provide limited evidence to indicate a relationship between 

uncomfortable indoor environment and migraines and severe headaches, mainly as a 

trigger among those who already experience these headaches. Noise and stress are also 

known triggers of migraines and severe headaches.

• Figure B5 in the Supporting Technical Information provides a visual display of these results.

Reproductive medical conditions were not more common among school employees 

compared with the U.S. population or a previous study of U.S. teachers

• A similar or lower proportion of school employees experienced endometriosis, uterine fibroids, 

hysterectomy, infertility, and miscarriage compared with the general U.S. population and other 

populations of employed women.

• We found no evidence that the reproductive medical conditions examined are related to working 

in the school.

• Figures B6–B7 in the Supporting Technical Information provides a visual display of these 

results.

To learn more about our results, go to Section B in the Supporting Technical Information
4

Our Recommendations

The Occupational Safety and Health Act requires employers to provide a safe workplace.

Potential Benefits of Improving Workplace Health and Safety:

 Improved worker health and well-being  Enhanced image and reputation 

 Better workplace morale  Superior products, processes, and services

 Easier employee recruiting and retention  May increase overall cost savings

The recommendations below are based on the findings of our evaluation. For each recommendation, 

we list a series of actions you can take to address the issue at your workplace. The actions at the 

beginning of each list are preferable to the ones listed later. 

We encourage the company to use a health and safety committee to discuss our 

recommendations and develop an action plan. Both employee representatives and 

management representatives should be included on the committee. Helpful guidance can be 

found in Recommended Practices for Safety and Health Programs at

https://www.osha.gov/shpguidelines/index.html. 

Recommendation 1: Prioritize the renovation or replacement of classroom 

ventilation systems

Why? Properly designed, installed, and maintained HVAC systems can prevent outdoor contaminants 

from entering the school via the outdoor air intakes of the ventilation system(s) and reduce indoor 

contaminants. Maintaining comfort parameters (temperature, humidity) at recommended levels has 

been shown to help resolve or improve symptoms among building occupants.

How? At your workplace, we recommend these specific actions:

Consult with a licensed professional mechanical engineer to conduct a 

comprehensive assessment of the school’s ventilation systems.

• The licensed professional mechanical engineer should have experience in the design of 

HVAC systems for educational environments including multiuse areas (such as 

classrooms, dining and kitchen areas, gymnasiums, and offices) and be familiar with 

buildings ventilated by both forced-air and unit ventilator-type systems.

o ANSI/ASHRAE Standard 62.1-2019 “Ventilation for Acceptable Indoor Air 

Quality” recommends a minimum ventilation rate of an outdoor air supply rate 

of 10 cubic feet per minute per person for classrooms. However, adequate 

ventilation rates can depend on occupancy, room size, outdoor air provided, and 

other building-related sources.
5

o ANSI/ASHRAE Standard 55-2020 “Thermal Environmental Conditions for 

Human Occupancy” reports human comfort to temperature and humidity levels 

and establishes a range of temperatures and humidity levels that are considered 

comfortable by 80% or more of the test subjects. The standard recommends:

 68.5 degrees Fahrenheit to 76 degrees Fahrenheit in the winter, and 

75 degrees Fahrenheit to 80.5 degrees Fahrenheit in the summer 

(assuming low air movement and 50% relative humidity) and,

 Relative humidity be kept at or below 65% in all seasons.

Ensure existing classroom unit ventilators work as designed.

• Do not block airflow around unit ventilators or supply air ducts.

• Reassess the existing preventive maintenance program. Regular inspections and proper 

maintenance will keep equipment functioning as designed, prolong service life, and save 

money over the life of the equipment.

• Audit classroom usage (e.g., activities, numbers of occupants) to understand demands 

on the space. Avoid using rooms not designed for occupants as classrooms or other 

occupied spaces.

• Keep windows closed to reduce the entrance of unfiltered, unconditioned air.

Recommendation 2: Start an indoor environmental quality management program

Why? This is a proactive approach that can help address the indoor environmental quality issues that 

have evolved over the past several years and prevent them from recurring. Good indoor 

environmental quality contributes to a favorable environment for students, performance of teachers 

and staff, and a sense of comfort, health, and well-being for all building occupants. The U.S. 

Environmental Protection Agency (EPA) provides guidance on indoor environmental quality in 

schools, found at Creating Healthy Indoor Air Quality in Schools at https://www.epa.gov/iaq-schools. 

Additional guidance can be found in the NIOSH/EPA document Building Air Quality: A Guide for 

Building Owners and Facility Managers. This document is available at 

https://www.epa.gov/sites/production/files/2014-08/documents/iaq.pdf.

A companion NIOSH/EPA guide, Building Air Quality Action Plan, discusses how to develop and 

assess an indoor environmental quality management program and is available at 

http://www.cdc.gov/niosh/docs/98-123/pdfs/98-123.pdf. 

Although no comprehensive regulatory standards specific to indoor environmental quality have been 

established, guidelines have been developed by organizations and agencies, including 

ANSI/ASHRAE, NIOSH, and EPA. These resources are available from the NIOSH indoor 

environmental quality topic page at http://www.cdc.gov/niosh/topics/indoorenv/. 
6

How? At your workplace, we recommend these specific actions:

Designate an indoor environmental quality manager or administrator 

with clearly defined responsibilities, authority, and resources to lead 

the program.

• The indoor environmental quality manager would be responsible for the following tasks:

o Understand the building’s structure and function and be able to communicate 

effectively with employees.

o Proactively identify and manage projects that might affect indoor environmental 

quality (e.g., redecoration, renovation, relocation of personnel).

o Oversee the activities of occupants and contractors that affect indoor 

environmental quality (e.g., housekeeping, pest control, maintenance, 

food preparation).

o Educate building occupants and contractors about their responsibilities in 

relation to indoor environmental quality.

o Encourage employees to report signs of moisture intrusion to the facilities 

maintenance staff.

o Speak for all employees and assist with communication. All staff should be made 

aware of the designee and how to submit concerns for investigation.

o Maintain and ensure effective and timely communication with occupants 

regarding indoor environmental quality.

Incorporate the following components of an effective indoor 

environmental quality management program:

• A formal system (preferably anonymous) for reporting building concerns.

o A mechanism to let staff know when and how the problem is addressed. 

o A plan for clear communication to all employees about the existence of the 

program and how to submit a concern.

• A fragrance-free workplace policy. Ensure the policy addresses perfumes and other 

scented personal care products, air fresheners, and potpourri.

o The American Lung Association publishes a sample fragrance-free school policy: 

http://action.lung.org/site/DocServer/fragrance-free-policy-sampleupdated.pdf. 
7

Recommendation 3: Improve communication to address employee concerns in 

the workplace

Why? We found that communication between the school administration and employees could be 

improved. Good communication is a key component to a strong health and safety program. It is 

important that school administration clearly communicate about hazards in the workplace and 

address concerns about potential hazards reported by employees.

How? At your workplace, we recommend these specific actions:

Communicate with employees about reported hazards and the steps being 

taken to address those concerns.

Encourage employees to report concerns about work-related symptoms or 

medical issues to their supervisor or another designee.

Encourage employees to seek evaluation and care (if needed) from a 

healthcare provider who is knowledgeable in occupational medicine for 

work-related medical concerns.

• The American College of Occupational and Environmental Medicine maintains a 

database of providers to help locate someone in your geographic area: 

https://acoem.org/Find-a-Provider. 

• It may be useful to provide the physician with a copy of this report. 

Recommendation 4: Create a pest management plan

Why? A workplace can have multiple health hazards that cause worker illness or injury. Similar to the 

ones identified above, these hazards can potentially cause serious health symptoms, lower morale and 

quality of life for your employees, and possibly increased costs to the school district. Although not 

the focus of our evaluation; employees reported and, we observed several indications of 

rodent infestation. 
8

How? At your workplace, we recommend these specific actions:

Hire a licensed exterminator to investigate the entire building for pests.

Consult existing resources to inform and implement your integrated pest 

management plan.

• For example, the Michigan Department of Agriculture and Rural Development provides 

resources for Integrated Pest Management Plans at 

https://www.michigan.gov/mdard/0,4610,7-125-1566_2405_37164---,00.html. 

Reevaluate food storage, consumption practices, and housekeeping after 

food consumption in classrooms.
Supporting Technical Information

Evaluation of Indoor Environmental Quality and 

Health Concerns Among Employees of a 

Public Elementary School

HHE Report No. 2019-0156-3382

October 2021
A-1

Section A: Workplace Information

Building 

The single-story, public elementary school was built in 1954. Two additions were made, one in the 

1960s and another in the 1990s. The school serves approximately 500 students in prekindergarten, 

kindergarten, and grades 1 through 5.

Employee Information

Number of employees at time of evaluation: 67

Median age: 39 years (range: 20–65 years)

Median tenure working at the school: 4 years (range: < 1–32 years)

Median hours/week spent in school: 40 hours (range: 3–55 hours/week)

Background

In 2015, employees saw evidence of water intrusion in the school. Employees also noted that multiple 

employees had or were experiencing migraines, thyroid disorders, and various reproductive medical 

conditions. They became concerned that these medical conditions could be associated with poor indoor 

environmental quality (IEQ) in their workplace.

Employees reported their concerns to school administrators in 2015. The same year, a new roof was 

installed; however, reports of water leaks inside the school continued. In 2016, the school 

administration contracted an environmental consultant to evaluate indoor air quality (IAQ). The 

consultant performed four evaluations between October 2015 and March 2019. Employees submitted 

this health hazard evaluation request after two employees suffered strokes, leading to increased concern 

about employees’ safety and health at work.
B-1

Section B: Methods, Results, and Discussion

Our objectives were to determine if the school had mold or other IEQ issues and if the medical and 

reproductive conditions of concern could be associated with the building.

Methods: Review of Prior Indoor Air Quality Consultant Reports

Four IAQ assessments were performed by an environmental consultant on behalf of school 

administrators and one IAQ assessment was performed by a different environmental consultant on 

behalf of the teachers’ union. We reviewed each assessment report to identify known problems and 

previously provided recommendations.

Results: Review of Prior Indoor Air Quality Consultant Reports

Prior Investigations Requested by School Administration 

October 2015

In response to employee concerns about the potential for mold growth in Rm 412 after a roof leak, 

school administration hired a consultant. The consultant performed a visual inspection, collected 

airborne mold samples, and measured temperature (°F), relative humidity (RH), carbon dioxide (CO2), 

and carbon monoxide (CO) levels in Rm 412 and other locations in and outside the building. The 

consultant reported the following:

• Multiple classrooms had materials and furniture blocking the front and tops of unit ventilators.

• Mold levels in the building ranged from 3,800 structures per cubic meter of air (sm3) to 

14,000 sm3. The mold level in Rm 412 was 14,000 sm3. The mold level outside the building was 

28,000 sm3. No growth or amplification sites of mold were found within the area of concern in 

the building.

• CO2 levels in the building ranged from 646 parts per million (ppm) (in Rm 113) to 1,318 ppm 

(in Rm 414); the CO2 level in Rm 412 was 1,303 ppm. The CO2 level outside the building was 

406 ppm.

• All CO levels were below instrument detection limits (≈1 ppm).

• Temperatures in the building ranged from 70.3°F (in Rm 412) to 73.9°F (in Rm 103). The 

temperature outside the building was 70°F. RH levels in the building ranged from 33.9% 

(in Rm 113) to 42.7% (in Rm 414). Outdoor RH was not reported. The temperature was 70.3°F 

and RH was 38.6% in Rm 412.

October 2016

In response to employee concerns about mold growth in carpets due to lingering moisture from 

cleaning performed during the summer, school administration hired a consultant. The consultant 

performed a visual inspection, collected airborne and surface mold samples, and measured temperature, 

RH, CO2, and CO levels in several locations in and outside the building. The consultant reported the 

following:
B-2

• Multiple classrooms had materials and furniture blocking the front and tops of unit ventilators.

• Mold levels in the building ranged from 2,100 sm3 (in the Library) to 43,000 sm3 (in Rm 322). 

The mold level outside the building was 41,000 sm3. Surface samples collected inside the 

building did not identify obvious signs of fungal growth or a reservoir.

• CO2 levels in the building ranged from 525 ppm (in Rm 321) to 2,685 ppm (in Rm 416). The 

CO2 level outside the building was 410 ppm. CO2 measurements were made in occupied areas, 

to the extent possible. CO levels were reported to be “very low” inside and 2 ppm outside.

• Temperatures in the building ranged from 72.0°F (in Rm 319) to 77.7°F (in Rm 202). The 

temperature outside the building was 76.0°F. RH levels in the building ranged from 42.3% 

(in Rm 107) to 57.2% (in Rm 314). The RH level outside the building was 54.3%.

January 2019

In response to reports that employees were “...experiencing health concerns...” associated with 

Rm 410, school administration hired a consultant. The consultant performed a visual inspection, 

collected airborne mold samples, and measured temperature, RH, CO2, and CO levels in Rm 410 and 

other locations in and outside the building. In addition, they measured volatile organic compounds, 

hydrogen sulfide, hydrocarbons, and percent oxygen levels. The consultant reported the following:

• Materials and furniture blocked the front and tops of the unit ventilator in Rm 410. In addition, 

there was a strong odor coming from under the sink, and a faint paint odor in the closet in 

Rm 410.

• Mold levels in the building ranged from 90 sm3 (in Rm 410) to 200 sm3 (in Rm 101). No mold 

was detected outside.

• Temperatures ranged from 67.5°F (in Rm 410) to 70.4°F (in the hall outside Rm 410). The 

temperature outside the building was –8°F. RH levels in the building ranged from 8.2% (in the 

hall outside Rm 410) to 11.8% (in Rm 410). The RH level outside the building was 0.5%.

• CO2 levels ranged from 410 to 487 ppm in room 410. The CO2 level outside the building was 

371 ppm. CO levels were low or below instrument detection limits (≈1 ppm) in all sampling 

locations inside and outside the building.

• Volatile organic compound sampling detected trace levels (described by the consultant as 

“...thousands of times less than Occupational Safety and Health Administration (OSHA) 

permissible exposure limits”) of ethanol and ethyl acetate (“...possibly from perfume or nail 

polish”).

• All hydrogen sulfide and hydrocarbon levels were below instrument detection limits (≈1 ppm).

• Percent oxygen measurements were 20.9% in all sampling locations inside and outside the 

building. All oxygen levels recorded were within established guidelines.

• “...these measurements were taken on a non-school day so do not represent measurements 

during occupied times.”
B-3

March 2019

In response to employee concerns about IAQ in the school, school administration hired a consultant. 

The consultant performed a visual inspection, collected airborne and bulk mold samples, airborne 

polychlorinated biphenyls samples, bulk water samples for lead and copper, and measured CO2 levels, 

focusing on the 400 wing of the building and outside the building. The consultant reported the 

following:

• Multiple classrooms had materials and furniture blocking the front and tops of unit ventilators.

• Mold levels in the building ranged from 210 sm3 (in 300 hallway) to 2,300 sm3 (in Rm 410). The 

mold level outside the building was 3,600 sm3. The bulk sample of insulation (from Rm 411) was 

reported as “not mold.”

• CO2 levels were not recorded, but real-time measurements were “...at times...” above 

2,000 ppm in Rm 410, Rm 412, and in “associated hallways during occupied times.”

• Lead and copper concentrations in water samples collected from drinking fountains were 

reported (by the laboratory) as below applicable EPA and State Action Levels.

• Polychlorinated biphenyls levels in the air in the building were reported as not detected.

Prior Investigation Requested by Employees 

May 2019

Employees hired a consultant to provide a second opinion about IAQ at the school. The employee 

consultant met with representatives of school employees, staff, and the school administration 

consultant. They reviewed past administration-initiated IAQ reports and performed a visual inspection 

of the building.

The consultant performed no sampling but encouraged administration to conduct (1) a health effects 

survey of employees, (2) an “enhanced” visual inspection of the school, including the tunnel system 

(crawlspace), (3) additional mold sampling, and (4) a detailed review of cleaning products and 

procedures.

Methods: On-site Building Evaluation

Visual Inspection

We inspected every room including classrooms, multipurpose areas, library, lunchroom, kitchen, 

gymnasium, and the administrative offices. We also inspected areas in the school not readily accessible 

to teachers or students, such as storage areas, the roof, and the crawlspace (referred to as tunnels in the 

consultants’ reports). We visually inspected ventilation systems and at least one of the three types of 

unit ventilators in the school.

Environmental Measurements 

We used TSI® Q-Traks to record temperature, RH, CO, and CO2 measurements in eight classrooms, 

the teacher’s lounge, and outside the building. We selected classrooms based on past complaints and 

past IAQ investigations. Measurements made in these classrooms were collected over the course of the 

school day (eight or more hours). Measurements made in other locations and outside the building were 
B-4

spot measurements. We compared these measurements with ANSI/ASHRAE guidelines when 

applicable.

NIOSH Dampness and Mold Assessment Tool 

We evaluated every room in the school using the NIOSH Dampness and Mold Assessment Tool 

(https://www.cdc.gov/niosh/docs/2019-114/pdfs/2019-114.pdf?id=10.26616/NIOSHPUB2019114). 

The tool refers users to the EPA document Mold Remediation in School and Commercial Buildings 

(www.epa.gov/mold/mold-remediation-schools-and-commercial-buildings-guide).

Results: On-site Building Evaluation

Visual Inspection

Lack of adequate space is an issue at the school, so some storage rooms had been converted to 

classroom use. We also observed classrooms crowded both with students and furniture.

Though we found signs of a lack of maintenance, we also observed recent maintenance including 

upgrades, repairs, and improvements to several HVAC units throughout the school. We observed 

evidence of past roof leaks. However, we found no evidence of current moisture or mold in any of the 

classrooms. We did see several stained ceiling tiles throughout the building but none of these stained 

surfaces were wet at the time of our visit.

The crawlspace had some water intrusion, but no mold growth. We observed a leaking hose bibb near 

the crawlspace on the outside the building, a potential source of the water in the crawlspace. We found 

two condensate drains in the courtyard that did not drain into their respective drainpipes. The school’s 

membrane-style flat roof had been replaced in 2015 and appeared in good condition, with little standing 

water and no debris that could potentially clog roof drains.

We saw scented air fresheners in use in a few locations. These can be a potential source of irritation, 

odor, and allergic reactions to some employees.

Heating, Ventilating, and Air-Conditioning

We inspected inside at least one of each type of unit ventilator in the building. A unit ventilator, also 

called a fan coil unit, is a simple ventilation system. Hot water from a central boiler was piped to each 

unit ventilator. A fan inside each unit ventilator circulated classroom air across the hot water lines to 

provide heating. As such, many of the unit ventilators could only provide heating and were unable to 

cool the air or control humidity.
B-5

In most classrooms, a unit ventilator was located on the 

exterior wall beneath an operable window, a design common 

in older schools (Figure B1). In some classrooms, the unit 

ventilator was in the ceiling (Figure B2).

Some (but not all) unit ventilators also had an outdoor air 

intake that could allow outdoor air to be mixed with 

recirculated room air. These units were paired with an 

exhaust fan to help move air though the classroom. Not all 

of these fans functioned. Consistent with the prior IAQ 

consultant reports, we found multiple classrooms had 

teaching supplies and/or furniture partially blocking unit 

ventilator air intakes and/or exhausts. In addition to 

affecting ventilation, the clutter on and around unit 

ventilators may also hinder housekeeping and maintenance 

activities.

The interiors of unit ventilators that we randomly 

checked were clean and had no visible evidence of 

microbial contamination. Some of the classroom unit 

ventilators had damaged or missing foam seals on the 

covers. Seals ensure the unit ventilator circulates air only 

after it has been drawn through the filter. The air filters 

in these units were also the correct size, properly 

installed, and appeared in good 

condition (Figure B3).

Maintenance personnel reported that all the ventilation 

systems in the school used minimum efficiency reporting 

value (MERV) 8 air filters, an air filter type often used in 

nonindustrial workplaces such as offices and schools. 

The air filters in the rooftop HVAC units were replaced 

twice per year, while those in the classroom unit 

ventilators were replaced three times per year, or as 

needed. 

Figure B1. A typical classroom unit 

ventilator. Photo by NIOSH.

Figure B2. Typical classroom ceilingmounted unit ventilator. Photo by 

NIOSH.

Figure B3. Classroom unit ventilator 

with access panel removed. Photo by 

NIOSH.
B-6

Environmental Measurements 

The results of environmental monitoring are presented in Table C1.

Carbon Monoxide

During our visit, CO concentrations in the building ranged from not detected to 1 ppm, well below the 

most restrictive occupational exposure levels (OELs) (data not shown).

Carbon Dioxide

During our visit, CO2 concentrations in the classrooms ranged from 419 to 2,566 ppm. The maximum 

CO2 concentration was well above the outdoor level.

Temperature and Relative Humidity

During our visit, temperature and RH measurements ranged from 67°F to 80°F and 33% to 57% RH. 

Temperature and RH measurements inside the building were outside (either above or below) 

ANSI/ASHRAE guidelines.

NIOSH Dampness and Mold Assessment Tool 

We used the tool to evaluate every room in the building. We assessed for mold growth and water 

damage using the following tool guidelines:

a. Damage or Stains – This refers to any water-related damage or stains identified per component. 

Damage could include peeling paint, efflorescence, rust, warping, and deteriorated or crumbling 

building materials. Stains could include discoloration caused by possible water leaks, flooding or 

condensation.

b. Visible Mold – Mold can include patches or spots that are colored differently than the 

underlying material (typically gray, brown, or black). Mold can appear fuzzy and can have a 

musty or earthy odor.

c. Wet or Damp – Wet or damp conditions could include visible signs of moisture, such as water 

beads or condensation, humidity, water leaks, or flooding.

We then scored each room. Scoring is based on the size of all affected areas combined. Individual sizes 

of each affected area are added together to obtain a combined size. The possible scores are as follows:

0 = No problem areas identified.

1 = The combined area of damage is the size of a standard sheet of paper (81⁄2′′ × 11′′) or smaller.

2 = The combined area of damage is greater than the size of a standard sheet of paper (81⁄2′′ × 11′′) 

and less than the size of a standard interior door (32′′ × 80′′).

3 = The combined area of damage is greater than the size of a standard interior door (32′′ × 80′′).

A score of 3 for Damage or Stains, Visible Mold, or Wet or Damp should trigger immediate attention 

to identify problem sources and to remediate. Likewise, a score of 3 for Mold Odor should trigger 

attention to identify areas of hidden mold. For example: a score of 1-0-0 means:

• 1 = The combined area of damage/stain observed is the size of a standard sheet of paper or 

smaller.
B-7

• 0 = No visible mold growth.

• 0 = No wetness or dampness.

Scores should also be used for comparison of rooms/areas over time to see if remediation works or if 

problems get worse.

Though we found signs of past water intrusion, we found no evidence of current water intrusion or 

mold growth in any of the rooms of the school. Figure B4 shows the results of our assessment. None 

of the scores were greater than 2.

Figure B4. NIOSH dampness and mold assessment results
B-8

Methods: Employee Interviews

During our site visit, we invited all current school employees to participate in voluntary, confidential 

medical interviews. Employees who were on leave or not available during our visit were invited to 

participate in a phone interview. We used the structured interviews to collect information from 

employees about employment history at the school, other jobs outside of the school, demographics, 

respiratory and general medical symptoms and conditions, reproductive medical history, and health and 

safety concerns related to their work. Employees who reported the following medical conditions were 

invited to sign a medical record release form to allow NIOSH staff to request their medical records if 

needed to confirm a diagnosis: migraines and severe headaches, stroke, thyroid conditions or cancer, 

infertility, uterine fibroids, and hysterectomy.

We limited the analysis of chronic (i.e., stroke and thyroid disorders) and reproductive medical 

conditions to female employees who participated in an interview and who had worked at least one week 

during the previous school year. Male employees were excluded from analysis of stroke, thyroid 

disorders, and infertility because the risk of these conditions is known to differ by sex and there was a 

small number of male employees (< 5). Male employees were excluded from analyses of other 

reproductive conditions because they are not at risk for experiencing the conditions. 

In the following sections we describe the information collected about symptoms and conditions in 

detail. Using this information, we estimated the percentage of participating employees experiencing a 

symptom or condition, referred to as prevalence.

General and Respiratory Symptoms 

We asked employees about the frequency of the following symptoms and whether the symptom 

improves, stays the same, or worsens when away from work.

• Dry, itching, or irritated eyes

• Stuffy or runny nose, or sinus congestion

• Sore or dry throat

• Headache

• Chest tightness

• Wheezing

• Cough

• Shortness of breath

• Dizziness or lightheadedness

• Nausea, upset stomach, or gastrointestinal (GI) upset

Using a similar approach as previous studies [Brightman et al. 2008; Malkin et al. 1996], we classified the 

symptom as frequent if a person experienced the symptom daily or weekly. We classified the symptoms 
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as work-related if a person reported that the symptom improved when away from work. We estimated 

the prevalence of frequent, work-related symptoms among interview participants. 

Migraines or Severe Headaches

We asked interviewees if they ever had a migraine. If the interviewee reported ever experiencing a 

migraine, we asked follow-up questions to understand when they first experienced migraines, frequency 

of migraines, if the migraine symptoms improve when away from work, whether a medical professional 

had provided a diagnosis, and whether any known triggers exist. We then asked the same set of 

questions about severe headaches, which we defined as a headache bad enough to disrupt daily activities 

that was not a migraine.

We estimated the prevalence of migraines or severe headaches within the previous three months. 

Concentrating on the previous three months allowed for comparison with existing U.S. population 

statistics, limited the potential for inaccurate recall of older events, and captured the first three weeks of 

the school year. We also examined the proportion of persons experiencing migraine or severe headache 

in the past three months who reported the symptoms got better when away from work.

Stroke and Thyroid Disorders 

We asked interviewees if a medical professional had ever told them that they had a stroke, a thyroid 

problem, or thyroid cancer. If an interviewee reported one of these conditions, we asked follow-up 

questions about details and timing of the diagnosis. We estimated the lifetime prevalence of stroke and 

individual types of thyroid disorders and the prevalence of each condition diagnosed after beginning 

work at the school.

Reproductive Medical Conditions 

We asked female employees questions about their menstrual and reproductive history to assess the 

prevalence of the following conditions.

Endometriosis 

We asked interviewees if a medical professional had ever told them they had endometriosis. We asked 

those reporting a diagnosis when their symptoms began. From this information, we estimated the 

lifetime prevalence of endometriosis and the prevalence of endometriosis with symptoms starting after 

beginning work at the school.

Uterine Fibroids

We asked interviewees if a medical professional had ever told them they had uterine fibroids. We asked 

those reporting a diagnosis when their symptoms began. From this information, we estimated the 

lifetime prevalence of uterine fibroids and the prevalence of uterine fibroids with symptoms starting 

after beginning work at the school.

Hysterectomy

We asked interviewees if they had ever had a hysterectomy. We asked those reporting a hysterectomy 

when it occurred and why it was performed. From this information, we estimated the prevalence of 

hysterectomy and the prevalence of hysterectomy occurring after beginning work at the school. We also 

examined the reasons for hysterectomy to identify any patterns.
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Infertility

Infertility is defined as a female having unprotected sexual intercourse with a male partner for 1 year or 

more without becoming pregnant [CDC 2014b]. We estimated the prevalence of infertility as the 

number of female employees reporting infertility divided by the total number of female employees of 

reproductive age (15–44 years old); estimating infertility in this way allowed us to compare the 

prevalence of infertility among female employees to the prevalence in the U.S. population. We 

estimated the lifetime prevalence of infertility and the prevalence of infertility that occurred for the first 

time after beginning work at the school.

Miscarriage

We asked interviewees about their pregnancy history. For each pregnancy we asked their age at the 

beginning of pregnancy, whether they were working at the school during the pregnancy, gestational age 

in weeks at the end of the pregnancy, and how the pregnancy ended (e.g., live birth, miscarriage). We 

estimated the prevalence of miscarriages as the number of reported miscarriages divided by the total 

number of reported pregnancies occurring while the mother was working at the school.

Employee Concerns

We asked interviewees the following questions:

• Is there something in your workplace that you think is causing health problems? If yes, please 

tell me more about it.

• Is there anything else you would like me to know that I haven’t asked you about?

We examined the answers to these open-ended questions and describe the themes observed in 

employees’ answers.

Statistical Analysis and Data Visualization

For each prevalence estimate described above, we estimated the Clopper-Pearson exact 95% confidence 

interval (CI). For miscarriage, we estimated the prevalence and 95% CI using generalized estimating 

equations to account for nonindependence of miscarriages experienced by the same woman. CIs are 

provided to show precision; the smaller the number of people included in the analysis, the wider the 

interval and the less precision we have. Because the occurrence of some conditions increases with 

increasing age, we attempted to either present estimates by age group or adjust for age; however, 

there were too few employees in each age group to provide stable estimates, so those results are not 

reported here. 

We identified previous studies and published estimates of the prevalence of each condition described 

above in the general U.S. population and other working populations as available. We qualitatively 

compared the prevalence of each condition to the prevalence found in other populations to determine 

whether the prevalence among school employees was less than, similar to, or greater than the 

prevalence in comparable populations.

To visualize these analyses, we created stock graphs showing the results from the employee interviews 

and how they compare with the U.S. population or relevant populations of employed U.S. women, 

when available.
B-11

Results: Employee Interviews

Among 67 employees of the school, 65 participated in an interview and are included in analysis of 

general symptoms. For analysis of health outcomes that take time to develop (i.e., stroke, thyroid 

disorders, reproductive health outcomes) we included the 58 female employees who participated in an 

interview and worked at the school for at least one week prior to the 2019–2020 school year. 

Among the 65 participating employees,

• > 90% identified as female;

• > 90% identified as non-Hispanic white;

• 54% (n = 35) were teachers, 23% (n = 15) were paraprofessionals, and 23% (n = 15) were 

administrators, school assistants, interventionists, or specialists; 

• 17% (n = 11) reported working another job outside of the school, including jobs in the service, 

education, recreation, and sales industries; 

• median age was 39 years (range: 20–65 years old); and,

• median time working at the school was 4 years (range: < 1–32 years) for a median 

40 hours/week (range: 3–55 hours/week) during the school year.

General and Respiratory Symptoms 

The percentage of frequent, work-related symptoms reported by school employees is shown in 

Table C2. Frequent, work-related headache was the most common symptom followed by stuffy or 

runny nose, or sinus congestion. The percentage of school employees reporting these two symptoms 

was similar to the percentage of office workers in buildings with IEQ complaints, and greater than the 

percentage of office workers in buildings with no known IEQ complaints. The prevalence of other 

symptoms among school employees was low, and similar to what has been reported by office workers 

in buildings with no known IEQ complaints. 

Migraines and Severe Headaches 

Approximately 40% (95% CI: 28%, 53%) of school employees reported a migraine or severe headache

during the previous three months (Table C3). This estimate was elevated compared with what has been 

reported among female U.S. teachers and paraprofessionals participating in a national study (24%) 

[CDC 2018a] and women in the general U.S. population (28%) [Smitherman et al. 2013]. However, only 

19% (95% CI: 10%, 31%) of female school employees met the criteria for potentially work-related 

migraines or severe headaches (meaning the migraine or severe headache improved when away from the 

school environment). 

Strokes and Thyroid Conditions 

No strokes were reported among participating employees. We are aware of reports of two strokes 

occurring among former employees of the school but are not able to assess medical outcomes among 

former employees accurately. 

Six of 58 current employees who worked at the school prior to the 2019–2020 school year reported a 

diagnosis of a thyroid condition (10%). Conditions reported included various types of hyper- and 
B-12

hypothyroidism; no employee reported a diagnosis of thyroid cancer. The lifetime prevalence of thyroid 

conditions reported by employees was similar to the prevalence of thyroid disorders in the 

U.S. population (1%–12% depending on the population) [American Thyroid Association, no date; 

Institute of Medicine 2003]. Only three employees reported that symptoms of their thyroid disorder 

began after starting work at the school.

Reproductive Medical Conditions 

The prevalence of the reproductive medical conditions evaluated are shown in Table C4. The 

prevalence of these conditions among participating employees was similar to the lifetime prevalence 

among U.S. women and populations of employed women. In addition, many symptoms of these 

conditions began prior to employment at the school.

Employee Concerns 

Approximately 46% of participating employees said they thought there was something in their 

workplace that is causing health problems; 25% said they did not think there was something in their 

workplace causing health problems; and 28% said they weren’t sure. The most mentioned 

environmental concerns were poor ventilation (67%), evidence of water intrusion (48%), mice (34%), 

poor cleanliness (33%), and odors (16%). Approximately 45% of employees were concerned about 

medical conditions either they had experienced or had seen coworkers’ experience; specific medical 

conditions mentioned included those evaluated here. In addition, employees described a stressful work 

environment due to concerns about workplace health and safety, poor communication between school 

administration and staff and between staff, an inability to take bathroom breaks when needed, and 

general pressures of serving as an educator.

Data Visualization

Figures B5–B7 show the percentage of participating school employees experiencing selected general and 

respiratory symptoms, migraines and severe headaches, and reproductive medical conditions compared 

with other populations. Figure B5, Graphs A–B show the percentage of participating school employees 

(n = 65) reporting frequent, work-related stuffy or runny nose, or sinus congestion and frequent, workrelated headache compared with observations from other studies of workers in buildings with and 

without IEQ complaints. Graph C shows the percentage of participating school employees (n = 64) 

reporting any migraine or severe headache and work-related migraine or severe headache during the 

previous three months compared with the percentage of the U.S. female population and U.S. female 

teachers and paraprofessionals experiencing at least one migraine or severe headache during a 3-month 

period. Figure B6, Graphs D–G show the percentage of participating school employees (n = 57) 

reporting ever receiving a diagnosis of endometriosis, uterine fibroids, and hysterectomy, and the 

percentage of participating school employees (n = 56) experiencing infertility compared with the 

percentage of the U.S. female population experiencing these medical conditions or procedures. Finally, 

Figure B7, Graph H shows the percentage of pregnancies experienced while employed at the school 

(n = 35) ending in miscarriage among participating school employees compared with the percentage of 

pregnancies ending in miscarriage in the U.S. female population and in a previous study of U.S. 

teachers. Estimates shown in Figures B5–B7 also appear in Tables C2–C4 along with citations for the 

comparison estimates.
B-13

Figure B5. Graphs (A–C) show the percentage of participating school employees who experienced the 

following symptoms or conditions as compared with other populations: (A) frequent, work-related 

stuffy or runny nose, or sinus congestion, (B) frequent work-related headache, and (C) any migraine or 

severe headache and work-related migraine or severe headache during the previous three months.
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Figure B6. Graphs (D–G) show the percentage of participating school employees who reported the 

following diagnoses or conditions as compared with other populations: (D) endometriosis, 

(E) uterine fibroids; (F) hysterectomy; and (G) infertility.
B-15

Figure B7. Graph H shows the percentage of pregnancies occurring while employed at the school 

reported to have ended in miscarriage compared with other populations.

Discussion 

We identified indicators of poor IEQ at the school during this evaluation. Classrooms, offices, and 

other spaces lacked appropriate ventilation to keep environmental parameters such as temperature and 

RH, in recommended ranges. Although we did not find mold present in the building, we did see 

evidence of past water intrusion. These IEQ deficiencies could be related to general symptoms 

(e.g., nasal irritation, headache) experienced by staff. Although employees were concerned about an 

excess of medical conditions including reproductive conditions, we did not find an excess among school 

employees compared with the U.S. population or other employed populations. In addition, we did not 

identify specific exposures that are known to cause these medical conditions.

Indoor Environmental Quality 

Our observations and recommendations about IEQ are consistent with the findings and 

recommendations provided by consultants hired by school administrators and employees. Below we 

provide context for our findings and recommendations to address IEQ at the school.

Heating, Ventilating, and Air-Conditioning

Even when new, some unit ventilators would be unable to meet ANSI/ASHRAE guidelines for 

temperature and RH control. Increased occupancy rates are an added challenge to these systems.

The amount of air required to be delivered to a given space by a ventilation system is based primarily on 

the number of people occupying the space, the type and amount of equipment used in the space, and 

the overall size of the space [ANSI/ASHRAE 2019].

One of the most common deficiencies we have found over many years of health hazard evaluations in 

nonindustrial indoor environments is the inadequate design, improper operation and/or maintenance of 

ventilation systems and other building components [Rosenstock 1996]. NIOSH investigators have 

found that correcting HVAC problems often reduces reported symptoms. Most studies of ventilation 

rates and building occupant symptoms have shown that rates below 20 cubic feet per minute per person 
B-16

are associated with one or more health symptoms [Seppänen et al. 1999]. Moreover, higher ventilation 

rates have been associated with decreases in the prevalence of symptoms [Seppänen et al. 1999].

An analysis of the published scientific literature showed that nonspecific symptoms such as headache, 

fatigue, and mucous membrane irritation increase as ventilation rates decrease [Fisk et al. 2009]. Studies 

in schools and office buildings have found a decrease in illness-related absences with increased 

ventilation rates [Mendell et al. 2011; Milton et al. 2000; Shendell et al. 2004]. Thus, improving HVAC 

operation and maintenance and increasing ventilation rates can improve symptoms without ever 

identifying any specific cause-effect relationships. We believe similar benefits would occur if ventilation 

is improved at this school. Additionally, improvements to ventilation are a key element of preventing 

the spread of viruses such as SARS-CoV-2, the virus that causes COVID-19.

Environmental Measurements

Carbon Monoxide

During our visit, CO levels were well below the most restrictive occupational exposure level.

CO is a colorless, odorless, tasteless gas produced by incomplete burning of carbon-containing 

materials (e.g., gasoline, wood, coal). Exposure to CO limits the ability of the blood to carry oxygen to 

the tissues by binding with hemoglobin to form carboxyhemoglobin (COHb) [ACGIH 2001; NIOSH 

1972, 1977, 1979, 2010; Proctor et al. 1988]. The initial symptoms of CO poisoning may include 

headache, dizziness, drowsiness, and nausea. These initial symptoms may advance to vomiting, loss of 

consciousness, and collapse if prolonged or high exposures are encountered. Coma or death may occur 

if high exposures continue.

Carbon Dioxide

During our visit, the maximum CO2 levels were well above outdoor levels in seven of the eight 

classrooms we measured. Elevated indoor CO2 levels could indicate potentially inadequate ventilation.

Outdoor air is delivered through the ventilation system and is necessary to dilute indoor air pollutants. 

Office machines, building materials, furnishings, cleaning products, and the building occupants 

themselves are potential sources of indoor air pollutants. CO2 is a normal constituent of exhaled breath 

and is not considered a building air pollutant. However, CO2 concentrations can be used as an easily 

measured surrogate for ventilation rates. It can be used as an indicator of whether enough outdoor air is 

being introduced into an occupied space for acceptable odor control and comfort. As the level of CO2

increases, the level of indoor contaminants may also be increasing. Recent studies have shown that the 

health effects associated with elevated CO2 levels are varied and may be associated with other factors 

[Fisk et al. 2019; Mishra et al. 2021; Persily and de Jonge 2017].

Temperature and Relative Humidity

During our visit, temperature and RH measurements inside the building exceeded ANSI/ASHRAE 

guidelines indicating inadequate thermal and humidity control.

The ANSI/ASHRAE Standard 55-2020, Thermal Environmental Conditions for Human Occupancy, 

specifies conditions in which 80% or more of the occupants would be expected to find the environment 

thermally acceptable [ANSI/ASHRAE 2020]. Assuming slow air movement and 50% RH, the operative 

temperatures recommended by ANSI/ASHRAE range from 68.5°F to 76°F in the winter, and from 
B-17

75°F to 80.5°F in the summer. The difference between the two is largely due to seasonal clothing 

selection.

ASHRAE Standard 62.1-2019, Ventilation for Acceptable Indoor Air Quality, requires that RH levels 

be designed to be limited to 65% or less for mechanical systems with dehumidification capability 

[ANSI/ASHRAE 2019]. For other mechanical system types or where spaces are not served by 

mechanical systems, Standard 62.1 has no humidity limitations. Excessive humidity can promote the 

growth of microorganisms and dust mites. The standard does not specify a lower humidity limit but

notes that nonthermal comfort factors such as skin drying, irritation of mucus membranes, dry eyes, 

and static electricity may place limits on acceptability of very low humidity environments. Some 

employees reported these symptoms.

Mold

Exposure to microbes is not unique to the indoor environment. No environment, indoors or out, is 

completely free from microbes, not even a surgical operating room. Microbes present in indoor air that 

are relevant to health include pollen and plant spores coming from outdoors; bacteria, fungi, algae and 

protozoa from both indoors and outdoors; and microbes and allergens spread from person to person, 

and from person to environment (including pet dander) [WHO 2009]. Dampness and inadequate 

ventilation lead to the growth of microbes and degrade building materials [WHO 2009]. Many buildings 

have episodes of water or moisture intrusion. The key to preventing microbial growth is to identify the 

source of moisture and to eliminate it [NIOSH 2012]. Moisture intrusion, along with nutrient sources 

such as building materials or furnishings, allows mold and other microbes to grow indoors, so it is 

important to keep the building interior and furnishings dry [NIOSH 2012]. Remediation of microbial 

contamination may improve IEQ conditions even though a specific cause-effect relationship is not 

determined. NIOSH investigators routinely recommend remediating observed water intrusion, 

dampness, and microbial contamination, and correcting situations that are favorable for microbial 

growth and bioaerosol dissemination [NIOSH 2012].

Although we did not find evidence of current water intrusion and related microbial growth, it is 

important that measures are taken to prevent water intrusion in the future to protect the health and 

safety of those spending time in the building [NIOSH 2012]. No exposure guidelines for mold in air 

exist, so it is not possible to distinguish between “safe” and “unsafe” levels of exposure. Healthy 

individuals are usually not vulnerable to infections from airborne mold exposure. However, people with 

weakened immune systems (those with diabetes, on chronic systemic steroid therapy, with cancer or 

acquired immune deficiency syndrome, among others) may be more vulnerable to infections by molds. 

Nevertheless, the potential for health problems is an important reason to prevent indoor mold growth 

and to remediate any indoor mold contamination. Moisture intrusion, along with nutrient sources such 

as building materials or furnishings, allows mold to grow indoors, so it is important to keep the building 

interior and furnishings dry. By preventing water intrusion and thereby microbial growth, the potential 

for exposure to mold or other microbes in the school environment will be limited.

No airborne exposure standards specific to the nonindustrial indoor environment exist. Likewise, no 

exposure guidelines for mold (or other microbes) in air exist, so it is not possible to distinguish between 

“safe” and “unsafe” levels of exposure. Therefore, measuring indoor environmental contaminants, such 
B-18

as mold or volatile organic compounds, has seldom proved helpful in determining the cause of 

symptoms. For this reason, we do not recommend sampling for mold and encourage redirecting 

resources toward improving ventilation systems.

Health Concerns 

The percentage of employees experiencing frequent, work-related headache, stuffy or runny nose or 

sinus congestion, or sore or dry throat was similar to the percentage of employees in buildings with 

known IEQ problems reporting these symptoms in previous evaluations [Brightman et al. 2008, 

Malkin et al. 1996]. These symptoms are nonspecific, meaning they can be caused by many things, and 

are common. For example, 86%–95% of the general population have one or more of these symptoms 

during any given 2- to 4-week period, and the average adult reports a minimum of one symptom every 

4–6 days [Barsky and Borus 1995]. Further, the average adult has two to three upper respiratory 

infections per year, also causing these nonspecific symptoms [Benninger et al. 2003]. 

Water intrusion with resultant microbial growth and lack of adequate ventilation are both associated 

with many of the symptoms reported by employees [Brightman et al. 2008, Malkin et al. 1996]. During 

our visit, ventilation deficiencies were almost ubiquitous throughout the school. While past water 

damage was isolated and limited and we did not see visible mold growth. Therefore, it is more likely that 

poor ventilation may be contributing to the occurrence of these nonspecific symptoms compared with

dampness, water damage, and mold growth. Low indoor RH is more likely in winter. Health complaints 

associated with indoor dryness include skin irritation; drying of the mucous membranes of the nose, 

mouth, and throat; nosebleeds; eye irritation; sore throat; and minor respiratory difficulties [Arundel et 

al. 1986; Berglund 1998].

We also found an elevated prevalence of migraines and severe headaches during the previous three 

months compared with U.S. studies of teachers and paraprofessionals and the general U.S. population 

[CDC 2018a; Smitherman et al. 2013]. However, only half of those migraines and severe headaches 

qualified as potentially work-related, meaning the migraines or severe headaches improved when 

employees were away from the school, indicating that something in the school environment may not 

fully explain this excess. 

Migraines and severe headaches are common in the United States, especially among women between 

the ages of 18 and 44 years [Lipton et al. 2001; Smitherman et al. 2013]. Approximately one in every 

four women will experience a migraine during their lifetime, and these symptoms can be disabling and 

burdensome, often interfering with productivity [Bigal et al. 2004; Moens et al. 2007; Smitherman et al. 

2013; Tietjen et al. 2012]. Migraines and severe headaches have a range of triggers that include foods 

and beverages, weather changes, hormonal changes (e.g., pregnancy, menstruation), and environmental 

factors [Friedman et al. 2009]. Factors in indoor environments (e.g., poor ventilation, out-of-comfort 

lighting, loud noise, odors) may serve as triggers in people who suffer from migraines or severe 

headaches [Tietjen et al. 2012]. In addition, previous work has shown that stress in the workplace may 

also trigger migraines and severe headaches in those who suffer from them [Tietjen et al. 2012]. Because 

migraines and severe headaches are common and can have many triggers [Smitherman et al. 2013], a 

link to any specific exposure at the school cannot be made with certainty. However, improving 
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ventilation, reducing odors by implementing a fragrance-free workplace policy, and addressing stressors 

in the work environment can help reduce migraine and severe headache triggers.

Many employees originally became concerned about health and safety of school staff following reports 

that two employees suffered strokes. Neither person reported to have experienced a stroke was still 

working at the school and therefore we were unable to investigate these reports further. We found no 

evidence of an excess of thyroid disease, infertility, endometriosis, uterine fibroids, hysterectomy, and 

miscarriages among current staff compared with the U.S. population and other working populations of 

women. We also did not identify any known causes of these conditions in the school environment. 

Information about the epidemiology of each of the reproductive conditions is provided in Section D. 

Many of these conditions are distressing, often occur without an obvious reason and are not openly 

discussed. Once people begin to discuss their experiences, the number of people experiencing a 

condition can seem overwhelming, even when occurring at a similar rate as in the U.S. population. 

When this happens at work, people may search for a cause of their conditions or symptoms in the work 

environment. However, care must be taken when attributing common symptoms or conditions to 

specific exposures because the occurrence of these conditions may not be related to a common, 

workplace cause. 

With few exceptions, concentrations of frequently measured chemical substances in the indoor work 

environment fell well below the recommended OELs published by NIOSH [NIOSH 2010], ACGIH 

[ACGIH 2021], and the American Industrial Hygiene Association (AIHA) [AIHA 2010], as well as the 

mandatory PELs set by OSHA [29 CFR 1910 (general industry)]. ANSI/ASHRAE has published 

recommended building ventilation and thermal comfort guidelines [ANSI/ASHRAE 2019, 2020]. 

ACGIH and AIHA have also developed a manual of guidelines for approaching investigations of 

building-related symptoms that might be caused by airborne living organisms or their effluents [ACGIH 

1999; AIHA 2008]. Other resources that provide guidance for establishing acceptable IEQ are available 

through EPA at https://www.epa.gov/indoor-air-quality-iaq and https://www.epa.gov/iaq-schools as 

well as the joint EPA/NIOSH document Building Air Quality: A Guide for Building Owners and 

Facility Managers. 

Limitations 

This evaluation is subject to several limitations. Industrial hygiene sampling can only document 

exposures and conditions in the locations evaluated and on the days the evaluation occurred. These 

results may not be representative of conditions in the past, during other days, or on other work sites. In 

addition, we were only able to document symptoms, conditions, and concerns reported to us during our 

interviews of current employees. We were not able to include former employees in our evaluation. We 

were told of a small number of employees who left work due to illness and we considered that 

information as part of our evaluation. However, if substantial numbers of employees left work because 

they were ill, this could affect our results. Additionally, many of the conditions and symptoms 

employees expressed concern about are complicated to diagnose and sensitive topics to discuss, making 

them difficult to measure both within employees and in the general population. This means that some 

people will be misclassified as having a condition when they don’t, or as not having a condition when 

they do. If this misclassification is not systematic, it should not change our conclusions. Finally, 
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although many of the conditions we examined are common, the population of school employees is 

small. Because of the small number of people experiencing each condition, we were not able to adjust 

for characteristics that relate to a person’s risk of a disease (e.g., age). This limited our ability to identify 

appropriate estimates from other populations for comparison.

Conclusions

Many of the symptoms reported by employees, such as headaches and nasal irritation, are common in 

the general population but are also associated with inadequate ventilation. In addition, it is also possible 

that inadequate ventilation combined with stressors in the work environment may trigger migraines or 

severe headaches among employees who experience these conditions. We found no evidence that other 

reported medical problems were occurring more frequently among school employees compared with 

other similar populations, or that these medical problems could be related to the school. Improvements 

to the school ventilation system, using building areas for their designed use, and improved 

communication between school administrators and staff should result in improved safety and health 

of employees. 
C-1

Section C: Tables

Table C1. Carbon dioxide, temperature, and relative humidity measurements

Location Carbon dioxide

(in ppm)

Temperature*

(in Fahrenheit)

Relative humidity†

(in percent)

 Low High Average Low High Average Low High Average

Rm 111 523 2,566 1,637 67 80 75 33 51 42

Rm 112 431 1,704 783 75 80 78 51 55 53

Rm 202 419 879 541 75 79 77 46 56 51

Rm 311 459 1,880 1,331 74 78 76 33 53 49

Rm 320 407 1,430 624 73 78 76 51 64 54

Rm 400 431 1,582 933 73 77 75 41 56 48

Rm 410 397 1,118 567 72 79 75 51 67 56

Rm 411 422 1,635 597 74 81 78 48 58 54

Lounge 373 1,089 576 75 81 78 40 56 45

Outside 363 406 378 68 79 74 37 72 54

* ANSI/ASHRAE recommends indoor temperatures of 68.5°F to 76°F in the winter, and 75°F to 80.5°F in 

the summer.

† ANSI/ASHRAE recommends indoor relative humidity be maintained at or below 65%.
C-2

Table C2. Percentage of school employees participating in an interview (n = 65) experiencing frequent, 

work-related symptoms compared with previous studies of office workers in buildings with and without 

indoor environmental quality (IEQ) complaints 

Frequent, work-related symptom* School employees Comparison groups 

working populations in buildings

 No. Percent (95% CI) With IEQ 

complaints† 

Without IEQ 

complaints‡ 

Headache§ 20 31% (20%, 43%) 25% 15%

Stuffy or runny nose, or 

sinus congestion

13 20% (11%, 31%) 22% 13%

Sore or dry throat 7 11% (4%, 21%) 16% 7%

Dry, itching, or irritated eyes 5 8% (3%, 17%) 30% 19%

Cough 3 5% (1%, 13%) 9% 5%

Dizziness or lightheadedness 3 5% (1%, 13%) 8% 3%

Chest tightness 3 5% (1%, 13%) 6% 2%

Shortness of breath 1 2% (0%, 9%) 5% 2%

Nausea, upset stomach, or 

GI upset

1 2% (0%, 9%) 5% 3%

Wheezing 1 2% (0%, 9%) 4% 2%

* Unrelated to an acute illness such as a cold or gastrointestinal infection. Frequent, work-related means a 

symptom that occurs at least weekly and gets better when away from work.

† Malkin et al. 1996

‡ Brightman et al. 2008

§ Excludes migraines and severe headaches.

Table C3. Percentage of school employees (n = 64) reporting a migraine or severe headache during the 

previous three months compared with published estimates from studies of employed women and the 

U.S. population 

Symptom School employees Comparison groups

 Total Work-related* Employed 

population of U.S. 

teachers and 

paraprofessionals† 

U.S. 

population‡ 

 No. Percent 

(95% CI)

No. Percent 

(95% CI)

Percent Percent

Migraines and severe 

headaches

25 40% 

(28%, 53%)

12 19% 

(10%, 31%)

24% 28%

* Work-related means the occurrence of migraine or severe headache improved when away from work.

† CDC 2018a 

‡ Smitherman et al. 2013
C-3

Table C4. Percentage of female school employees reporting a reproductive medical condition compared with previous 

studies of women in the U.S. population and other employed populations

Self-reported 

reproductive 

medical 

condition 

School employees Comparison groups

 Lifetime Symptoms began after 

employment at the school

U.S. female 

population* 

Employed 

women† 

 No. 

interviewed

No. Percent 

(95% CI)

No. 

interviewed

No. Percent 

(95% CI)

Percent Percent

Endometriosis 57 8 14% 

(6%, 26%)

51 3 6% 

(1%, 16%)

10% — 

Uterine fibroids 57 7 12% 

(5%, 24%)

53 4 8% 

(2%, 18%)

9%–25% — 

Hysterectomy‡ 57 8 14% 

(6%, 26%)

56 7 13% 

(5%, 24%)

10% — 

Infertility§ 56 11 20%

(10%, 32%)

51 6 12% 

(4%, 24%)

6%–16% 16%

Pregnancy 

outcome

— — — No. 

pregnancies

No. Percent 

(95% CI)

— — 

Miscarriage — — — 35 6 17% 

(8%, 36%)

19% 25%

* Endometriosis estimate [Eisenberg et al. 2018]; uterine fibroids estimates [Marsh et al. 2018; Stewart et al. 2017; 

Yu et al. 2018]; hysterectomy estimate [Brett et al. 1997], infertility estimates [CDC 2014a,b; Gleason et al. 2019]; 

miscarriage estimate [Rossen et al. 2018].

† Infertility estimate [Katon et al. 2014]; miscarriage estimate [Lawson et al. 2012; Grajewski et al. 2015]. 

‡ Reasons for hysterectomy reported by school employees included uterine fibroids, heavy periods, other 

complications. 

§ Infertility is defined as having unprotected sex with a male partner for 1 year or more without becoming pregnant 

[CDC 2014b]. Reasons for infertility reported by school employees included endometriosis, polycystic ovary syndrome 

(PCOS), and not ovulating regularly. Some employees reported more than one reason.
D-1

Section D: Epidemiology of Selected Reproductive Outcomes

Endometriosis 

Endometriosis is a condition where tissue that normally lines the uterus grows outside the uterus [CDC 

2018b; Office of Women’s Health 2019a]. When this tissue grows outside the uterus, it can cause pain 

(typically in the abdomen, lower back, or pelvic area), pain during urination or intercourse, heavy 

periods, fatigue, and constipation [Eisenberg et al. 2018; Office of Women’s Health 2019a]. 

Endometriosis can also cause infertility; for some women, having trouble getting pregnant may be the 

first sign of the condition. 

Endometriosis is thought to affect more than 6.5 million women (11% of women) in the United States 

between the ages of 15 and 44 years old [Office of Women’s Health 2019a]. Depending on the 

population, up to 16% of women may have endometriosis [Fuldeore and Soliman 2017]. However, the 

true prevalence of endometriosis in the United States may be higher because the diagnosis can be 

complicated to make and is at times overlooked [Eisenberg et al. 2018; Giudice and Kao 2004]. 

The cause of endometriosis is not well understood [Office of Women’s Health 2019a]. However, women 

who have never had children, menstrual periods that last more than 7 days, short menstrual cycles 

(27 days or fewer), a family member with endometriosis, or a health problem that blocks the normal flow 

of menstrual blood from the body may be more likely to develop endometriosis. Researchers have 

examined associations between exposure to environmental chemicals and endometriosis; specifically, 

estrogen-like compounds have been suggested as a potential cause [Giudice and Kao 2004]. However, 

there is no definitive evidence linking chemical exposure to risk of endometriosis.

More information about endometriosis can be found at: 

https://www.womenshealth.gov/a-z-topics/endometriosis. 

Uterine Fibroids

Uterine fibroids are tumors made up of muscle cells that grow in the wall of the uterus [Office of 

Women’s Health 2019b; Stewart et al. 2017]. Not all women with fibroids have symptoms [Office of 

Women’s Health 2019b; Stewart et al. 2017]. Women who do have symptoms may experience pain and 

heavy menstrual bleeding, feeling “full” in the lower abdomen, frequent urination or incontinence, 

constipation, pain during intercourse, and lower back pain. Fibroids can also result in reproductive 

problems such as infertility, miscarriage, or early labor. 

Uterine fibroids are the most common noncancerous tumors in women of childbearing age and are 

common in the United States [Office of Women’s Health 2019b; Stewart et al. 2017]. Approximately 

20%–80% of women develop fibroids by the time they are 50 years old; fibroids occur most commonly 

in women in their 40s and 50s. The prevalence is difficult to estimate because many women may have 

fibroids but no symptoms. 

The cause of fibroids is unknown. The risk of fibroids increases with increasing age until a woman 

reaches her 60s, when risk declines because of menopause [Stewart et al. 2017]. Fibroids are more 

common among Black women than White women. In addition, having a family history of fibroids, 
D-2

being overweight, or eating a diet rich in red meat and ham are factors associated with a higher risk of 

fibroids [Office of Women’s Health 2019b; Stewart et al. 2017]. Some reproductive factors (e.g., giving 

birth, time since last birth), use of some contraceptives, and smoking are associated with a reduced risk 

of fibroids [Stewart et al. 2017]. 

Researchers have examined associations between exposure to endocrine-disrupting chemicals, or 

chemicals that mimic or interfere with the body’s hormones known as the endocrine system, and 

fibroids [Katz et al. 2016; NIEHS 2021]. However, there is no definitive evidence linking chemical 

exposure to risk of fibroids.

More information about uterine fibroids can be found at: 

https://www.cdc.gov/reproductivehealth/womensrh/healthconcerns.html#Fibroids%20. 

Hysterectomy

Hysterectomy is the surgical removal of the uterus; sometimes the cervix, ovaries, and fallopian tubes 

are also removed [CDC 2020; Whiteman et al. 2008]. Hysterectomies are very common—1 of 3 women 

in the United States has had a hysterectomy by age 60.

Hysterectomies are performed to relieve symptoms associated with gynecologic conditions, for 

example, endometriosis or uterine fibroids, or to treat conditions including uterine prolapse (when the 

uterus drops into the vagina); cancer of the uterus, cervix, or ovaries; vaginal bleeding that persists 

despite treatment; or chronic pelvic pain [Medline 2021]. 

More information about hysterectomy can be found at: 

https://www.cdc.gov/reproductivehealth/womensrh/index.htm and 

https://medlineplus.gov/hysterectomy.html. 

Infertility 

Infertility means not being able to get pregnant after 1 year of trying [CDC 2014b, 2020]. For clinical 

purposes, if a woman is 35 years old or older, infertility may be based on 6 months of trying to become 

pregnant. Women who can get pregnant but are unable to stay pregnant may also be considered infertile. 

Infertility can occur because of factors affecting either the male or female partner, or both partners. 

Previous studies in the United States have found that between 6% and 18% of couples experience 

infertility (do not achieve pregnancy within 12 months of trying) [CDC 2014b; Gleason 2019; Thoma 

2013]; the estimates vary based on study methodology and the population studied. About 10% of 

women (6.1 million) in the United States aged 15–44 years have difficulty getting pregnant or staying 

pregnant [CDC 2020]. 

Age is one of the most important factors affecting fertility [CDC 2014b]. Among women who have not 

given birth, the percentage experiencing infertility increases with increasing age, from 7%–9% among 

those 15–34 years old to 25% among those 35–39 years old, and 30% among those 40–44 years old 

[CDC 2014b]. Older men may also contribute to infertility through reductions in the quality and 

quantity of sperm produced. 

Other factors that can affect fertility include genetic abnormalities, acute and chronic diseases, treatments 

for certain conditions, behavioral factors, and exposure to environmental, occupational, and infectious 
D-3

agents. Some known hazards that can affect fertility or disrupt the menstrual cycle or sex hormone 

production in women include cancer treatment drugs, heavy metals, ionizing radiation (including x-rays), 

nitrous oxide, some pesticides, carbon disulfide, and polychlorinated biphenyls (PCBs).

More information about infertility can be found at:

https://www.cdc.gov/reproductivehealth/womensrh/index.htm and 

https://www.cdc.gov/niosh/topics/repro/default.html. 

Miscarriage 

Pregnancy loss is the unexpected loss of a fetus before the 20th week of pregnancy [NIH 2017]. 

Pregnancy loss is sometimes called miscarriage, early pregnancy loss, mid-trimester pregnancy loss, 

fetal demise, or spontaneous abortion. Stillbirth is used to describe the loss of a fetus after 20 weeks 

of gestation.

Pregnancy loss is common; studies have documented that between 10% and 28% of recognized 

pregnancies end in pregnancy loss [NIH 2017; Rossen 2018]. This may be an underestimate because 

pregnancy loss can occur before a woman's pregnancy is confirmed by a health care provider or 

pregnancy test, or even before a woman knows she is pregnant.

It is difficult to identify the causes of pregnancy loss (miscarriage) because it can occur before 

confirmation of a pregnancy. A majority of pregnancy loss happens when genetic abnormalities are 

present in the embryo [Krieg 2016]. Known risk factors for pregnancy loss include older maternal age, 

hormonal imbalances, uterine abnormalities, and immunological interactions. Lifestyle factors such as 

tobacco and alcohol use are also thought to contribute to miscarriage. 

Studies have examined the association between occupational or environmental exposures and 

pregnancy loss [Krieg 2016; Patelarou and Kelly 2014; Silbergeld and Patrick 2005]. Specific 

occupational exposures that may be associated with reproductive outcomes such as miscarriage include 

anesthetic gases, antineoplastic (chemotherapy) drugs, antiviral drugs, sterilizing agents (disinfectants), 

and ionizing radiation [Lawson 2012]. 

Exposure to some chemicals (for example, endocrine-disrupting chemicals) or heavy metals either in the 

environment or while at work is associated with miscarriage [Hertz-Picciotto 2000; Krieg 2016]. 

Examples of such chemicals include pesticides (e.g., DDT), bisphenol-A (BPA), PCBs, phthalates and 

their metabolites, and lead. A person may be exposed to these chemicals through the environment and 

consumer products, or through their work. 

Some evidence suggests that exposure to air pollution may be associated with an increased risk of 

miscarriage; however, this relationship and the specific components of air pollution that may affect a 

pregnancy remains unclear [Silbergeld and Patrick 2005]. In addition, a recent review of published 

studies found that more research is needed to fully understand whether indoor exposures are associated 

with an increased risk of reproductive outcomes including miscarriage [Patelarou and Kelly 2014].

More information about miscarriage and pregnancy loss can be found at: 

https://www.nichd.nih.gov/health/topics/pregnancyloss/conditioninfo. 
E-1

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