Health Hazard Evaluation Report 2010-0001-3295 Page 1

Evaluation of Occupational Exposures at an 

Insect Rearing Facility

Report No. 2010-0001-3295

November 2017

John D. Gibbins, DVM, MPH

Scott E. Brueck, MS, CIH

David Sylvain, MS, CIH, 1992–2012

Aalok Oza, MPH
Page 2 Health Hazard Evaluation Report 2010-0001-3295

Contents

Highlights...............................................i

Abbreviations ..................................... iii

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

Methods................................................ 3

Results and Discussion........................ 5

Conclusions........................................ 17

Recommendations............................. 17

Appendix A......................................... 21

Appendix B......................................... 24

Appendix C......................................... 29

References.......................................... 31

Acknowledgements........................... 35

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material.

The cover photo is a close-up image of sorbent tubes, which are used by the HHE 

Program to measure airborne exposures. This photo is an artistic representation that may 

not be related to this Health Hazard Evaluation. Photo by NIOSH.
Health Hazard Evaluation Report 2010-0001-3295 Page i

We evaluated employees’ 

exposures to formaldehyde 

and inhalable particulate 

matter in the insect rearing 

facility. Employees’ exposures 

to formaldehyde in the egg 

preparation area were above 

occupational exposure limits. 

Inhalable particulate exposures 

from insect debris were highest 

during moth collection and 

tray scraping. Some employees 

reported health symptoms 

and had medical evidence that 

suggested potential allergy, 

occupational asthma and lung 

obstruction. We recommended 

modifying the ventilation 

systems to improve capture 

and removal of inhalable 

particulates containing 

allergens and irritants.

Highlights of this Evaluation 

The Health Hazard Evaluation Program received a request from a federal agency on behalf 

of employees who worked at an insect rearing facility. Managers and employees were 

concerned about potential exposures to chemicals such as formaldehyde and bleach, insects, 

insect debris, and overall indoor environmental quality at the facility. 

What We Did

● We visited the facility in November 2009, May 2010, and August 2010. 

● We interviewed employees about their work, their health, and their concerns. 

● We reviewed health questionnaire results and 

lung function testing done by a contractor hired 

by the employer. 

● We took personal air samples to measure 

employees’ exposures to particulates. 

● We took area air samples to look for moth scales 

and other insect debris.

● We took personal and area air samples for 

formaldehyde during egg preparation 

and disinfection. 

● We observed engineering controls, ventilation, 

work practices, and personal protective 

equipment use. 

What We Found

● Employee exposures to formaldehyde during 

egg preparation and disinfection were above 

occupational exposure limits.

● Work procedures and practices could increase 

the potential for formaldehyde in the air and 

skin exposure to formaldehyde. 

● Employees’ exposures to airborne particulates 

were low, except during moth pouring, work in 

the egg production room, and tray scraping.

● Local exhaust ventilation in the egg production room, during moth pouring, and during 

tray scraping was not effective. 

● Employees reported health symptoms that could be caused by exposure to workplace 

allergens such as insects, insect debris, moth scales, chemicals, insect diet ingredients, 

and latex gloves. 
Page ii Health Hazard Evaluation Report 2010-0001-3295

● Some employees had changes on their lung function tests that suggested occupational 

asthma and lung obstruction. 

What the Employer Can Do

● Improve the performance of the lab hood and procedures during egg preparation and 

disinfection to reduce airborne formaldehyde exposures.

● Raise the platform for employees who place egg rings in formaldehyde tanks. 

● Improve the local exhaust ventilation in egg production and during moth pouring and 

tray scraping. 

● Ensure employees consistently use personal protective equipment. 

● Replace latex gloves with nitrile gloves to eliminate a potential allergen source. 

What Employees Can Do

● Carefully handle and pour ingredients from bags to minimize dust exposures. 

● Use a vacuum with high efficiency particulate air filters instead of compressed air to 

clean work areas, clothing, or personal protective equipment. 

● Always wear personal protective equipment that is advised or recommended for your 

work area. 

● Tell your supervisor and your doctor if you have health concerns you think are related 

to work. 

● Participate in all training about workplace hazards and respirator fit testing. 
Health Hazard Evaluation Report 2010-0001-3295 Page iii

Abbreviations

ACGIH® American Conference of Governmental Industrial Hygienists

CFR Code of Federal Regulations

CO2 Carbon dioxide

FOH Federal Occupational Health

FEV1 Forced expiratory volume in one second

fpm Feet per minute

FVC Forced vital capacity

HVAC Heating, ventilation, and air-conditioning

IOM Institute of Medicine

LEV Local exhaust ventilation

mg/m3 Milligrams per cubic meter

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PBWRF Pink bollworm rearing facility

PEL Permissible exposure limit

PPE Personal protective equipment 

ppm Parts per million

REL Recommended exposure limit

TLV® Threshold limit value

TWA Time-weighted average
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Health Hazard Evaluation Report 2010-0001-3295 Page 1

Introduction

The Health Hazard Evaluation Program received a request from the United States 

Department of Agriculture (USDA) on behalf of employees who worked at a pink 

bollworm rearing facility (PBWRF). Managers and employees were concerned about indoor 

environmental quality and possible development of respiratory problems and allergies from 

exposures to chemicals, insects, and insect debris. We visited the PBWRF in November 2009, 

May 2010, and August 2010 to evaluate employee exposures and learn more about health 

concerns. We sent union representatives, Federal Occupational Health (FOH) representatives, 

and PBWRF managers an interim letter in December 2009 that summarized our findings 

and recommendations. The PBWRF sent us a copy of its action plan to address our initial 

findings in December 2009. This report summarizes our findings and recommendations based 

on the conditions at the time of our evaluation. 

Background and Process Description

The PBWRF raised a single species of moth, Pectinophoa gossypiella (pink bollworm). 

Moths and butterflies belong to the insect order Lepidoptera. Species in this order have 

been associated with contact dermatitis, urticaria, and respiratory irritation and asthma in 

occupational and non-occupational settings [Centers for Disease Control and Prevention 

1984; Redd et al. 2007; Suarthana et al. 2012]. The moths reared at this facility were 

sterilized by irradiating them with cobalt 60. Sterile moths were subsequently released from 

aircraft into cotton fields as the Sterile Insect Technique component of the International Pink 

Bollworm Eradication Program. Additional information on the pink bollworm eradication 

program can be found at http://www.cdfa.ca.gov/plant/ipc/pinkbollworm/pbw_hp.htm.

At the time of our evaluation the facility was staffed by 25 employees year-round and an 

additional 47 seasonal employees. The seasonal employees typically worked from March to 

October to coincide with the increased need for moths during the cotton growing season. At the 

time of our evaluation between 20 and 26 million moths were produced daily during the cotton 

growing season; the facility was designed to produce approximately 15 million moths daily. 

Smaller numbers of moths (approximately 300,000 per day) were reared during the off season 

to maintain a continuous supply of bollworms on the basis of the lifecycle shown in Figure 1.
Page 2 Health Hazard Evaluation Report 2010-0001-3295

Figure 1. The 25 to 35 day life cycle of the pink bollworm. Figure by NIOSH.

Moth production was divided into two areas: “dirty” and “clean.” The dirty area refers to 

the part of the PBWRF where scales from moth wings (moth scales) were released during 

operations. The dirty area was maintained under negative pressure relative to surrounding 

areas to contain moth scales. The clean area refers to locations within the PBWRF where 

adult moths and scales should not be found. This arrangement was necessary to protect the 

health of the moth colony and ensure adequate moth production. Adult moths and scales 

can contain pathogens that can infect the other bollworm life stages and lead to death and 

decreased production. The facility had detailed sanitation and pest management protocols 

to address this concern. Floor to roof fire walls separated the administrative office area from 

the adjacent clean moth production area. The facility did not have a plenum or air exchange 

between the administrative office and production areas. 

Table 1 summarizes work processes and work areas within insect production and insect 

production support. A detailed description of the work areas is found in Appendix B. 

“Mandatory” and “advised” personal protective equipment (PPE) requirements varied by 

work location and are summarized in Appendix C.
Health Hazard Evaluation Report 2010-0001-3295 Page 3

Table 1. Work processes and work areas within insect 

production and insect support 

Insect production Insect production support

Egg preparation Diet weight room

Egg infestation Kitchen

Dark room Hexcel cleaning

Cutout room Cardboard cleaning

Hexcel® stripping Tray scraping

Egg production Quality control

Moth production and 

collection

Maintenance

Moth irradiation Supervisor

Moth packaging and shipping

Methods

The objectives for this evaluation were the following: 

1. Measure airborne exposures to formaldehyde and inhalable particulates.

2. Identify whether insect debris was present in air samples.

3. Evaluate engineering controls, work practices, and PPE use during moth production.

4. Identify potential work-related employee health concerns.

5. Determine if employees had changes in lung function that could be related to work.

Formaldehyde

In May 2010, we collected task-based personal air samples for formaldehyde on two 

employees disinfecting insect eggs. We collected one area air sample for formaldehyde in each 

of the two egg preparation rooms where egg rings were immersed in open tanks that contained 

54 gallons of 9% formaldehyde. Air samples were collected and analyzed according to 

National Institute for Occupational Safety and Health (NIOSH) Method 2016 [NIOSH 2016]. 

Inhalable Particulate Matter

In August 2010, we collected task-based or partial shift inhalable particulate air samples on 

employees during potentially dust-generating work activities in the insect diet weight room, 

kitchen, Hexcel stripping room, south cutout room, north cutout room, moth collection 

coolers or rooms, egg production room, moth packing and shipping rooms, irradiation room, 

and tray scraping room. Inhalable particulate matter comprises particles that are hazardous 

when deposited anywhere in the respiratory tract. The 50% cut point for inhalable particulate 

matter is 100 micrometers aerodynamic diameter [ACGIH 2017]. The samples were collected 

on Institute of Medicine (IOM) samplers with polyvinyl chloride filters and analyzed 
Page 4 Health Hazard Evaluation Report 2010-0001-3295

gravimetrically according to NIOSH Method 0600 [NIOSH 2016]. We had conducted similar

personal sampling for inhalable particulate matter in May 2010; however, due to laboratory

errors (e.g., negative weight gain of samples) the sample results were rejected and not reported.

Scanning Electron Microscopy

We collected nine area air samples in May 2010 for analysis by scanning electron microscopy 

to identify whether insect debris was present during potentially dust-generating work 

activities. These samples were collected in the same locations where we also collected the 

inhalable particulate matter personal samples, except for the Hexcel stripping room and 

irradiation room. The area samples were collected on three-piece air sampling cassettes 

containing 0.8-micrometer pore size polycarbonate filters at a flow rate of 2 liters per 

minute. Portions of each air sample filter and a bulk sample of moth scales and insect debris 

were placed onto carbon-taped stubs and then carbon coated. A Tescan scanning electron 

microscope equipped with a Gresham light element energy dispersive spectrometer and 

an IXS digital imaging system was used to examine the air sample filter and bulk samples. 

Photomicrographs were also taken of each sample. 

Local Exhaust Ventilation and Carbon Dioxide 

Measurements

We measured air velocities at the face of local exhaust ventilation (LEV) hoods using a TSI®

Velocicalc Plus® at operations where we observed that airborne dust capture appeared to be

insufficient. These operations included diet weighing, kitchen, Hexcel sheet stripping, moth 

pouring/collection, packing, and tray scraping. On the basis of the hood face velocities and the

distance from the hood that work activities were done, we estimated capture velocities. We used

a TSI Q-Trak® to take spot check measurements of carbon dioxide levels in the facility.

Medical Evaluation

We held confidential medical interviews with full-time employees in November 2009 at the 

end of the production season to discuss their work practices and health concerns. On the basis 

of our initial findings and observations, we returned in May 2010 to further evaluate employee 

health. During this visit we worked with an FOH physician who provided medical services for 

facility employees. FOH personnel held an in-service training with employees about potential 

workplace hazards and the spirometry (lung function testing) process. FOH personnel 

administered a brief questionnaire in English or Spanish based on the employees’ personal 

preference to determine if they were medically qualified for spirometry participation. FOH did 

preshift and postshift spirometry on consenting full-time and seasonal production workers. 

The NIOSH investigator and FOH physician developed a brief questionnaire in English and 

Spanish on job duties and health symptoms; FOH personnel administered this questionnaire 

after spirometry was completed. FOH personnel repeated the spirometry questionnaire and 

spirometry in September 2010. FOH provided spirometry results and interpretation by letter in 

English and Spanish to individual participants in November 2010. FOH provided a summary 

of spirometry and questionnaire results and interpretation to facility managers and federal 

agency health and safety officials in December 2010.
Health Hazard Evaluation Report 2010-0001-3295 Page 5

The spirometry tests measured the amount of air participants could forcibly exhale from their 

lungs. The volume of air expelled in the first second (FEV1) was compared to the total lung 

volume exhaled (FVC) and expressed as a ratio (FEV1/FVC). This ratio for participants was 

compared to spirometry standards for “normal” individuals using a mathematical formula that

calculated expected results based on the same ethnicity, age, sex, and height of participants. 

This ratio was expressed as a percentage with a FEV1/FVC ratio of ≤ 70% considered less than 

optimal for the purposes of this evaluation. Additionally, spirometry tests were done on the 

same individual at the beginning and end of the work shift when possible; a decrease of FEV1

of greater than 10% preshift vs. postshift was considered evidence of a workplace exposure or 

personal exposure (smoking) that resulted in lung obstruction. A decrease of FEV1 between 5% 

and 10% with symptoms of cough, chest tightness, or wheezing during the shift was considered 

potential evidence of a work-related change in lung function. 

Results and Discussion

Formaldehyde

Task-based personal air sampling results for formaldehyde during egg preparation and 

disinfection in rooms 163 and 164 are shown in Table 2. These air sampling results, collected 

for 101–134 minutes, show that employees’ exposures to formaldehyde were above the 

NIOSH ceiling limit of 0.1 parts per million (ppm). Employees’ exposures would also be 

above the NIOSH recommended exposure limit (REL) of 0.016 ppm, as an 8-hour timeweighted average (TWA), even if employees had no additional formaldehyde exposure 

during other work activities. Personal exposures, averaged over the sampling period, were 

not above the American Conference of Governmental Industrial Hygienists (ACGIH) ceiling 

limit. However, it is possible that exposures could at times exceed the ACGIH ceiling limit 

for formaldehyde. The Occupational Safety and Health Administration (OSHA) has an action 

level of 0.5 ppm and a permissible exposure limit (PEL) of 0.75 ppm for formaldehyde. Both 

of these limits are 8-hour TWAs. OSHA also has a short-term exposure limit of 2 ppm, which 

is the maximum exposure allowed over a 15-minute duration. Because our samples were 

substantially greater than 15 minutes duration and substantially less than 8-hours duration, 

we cannot compare our results directly to the OSHA limits. However, on the basis of these 

results, if employees had performed these tasks for an entire work shift their exposures to 

formaldehyde would likely be below the OSHA limits. Area sampling results, averaged 

over a 4-hour period during treatment and preparation of egg rings, showed a formaldehyde 

concentration of 0.12 ppm near the formaldehyde tanks in room 163 and a concentration of 

0.098 ppm near the drying racks in room 164. 
Page 6 Health Hazard Evaluation Report 2010-0001-3295

Table 2. Task-based personal air sampling results for formaldehyde during egg preparation and 

disinfection (May 2010)

Location/Activity Sample duration

(minutes)

Concentration

(ppm)

Employee 1: Rooms 163 and 164

Treating and preparing egg rings 

102 0.21

134 0.18

Employee 2: Rooms 163 and 164

Treating and preparing egg rings 

101 0.17

136 0.14

NIOSH ceiling limit 0.1

ACGIH ceiling limit 0.3

We observed procedures and work practices during the egg disinfection operation that 

could potentially increase air contaminant levels and the potential for dermal contact with 

formaldehyde. Employees had to open the fume hood sash all the way to be able to place the 

spindles of egg rings into the formaldehyde solution. Opening a lab hood sash beyond the 

recommended maximum height reduces the face velocity of the hood and thus the ability 

of the hood to contain formaldehyde gas. We observed that employees had to reach up and 

over the edge of the formaldehyde tanks to submerge the spindles of the egg rings. Shorter 

employees had difficulty performing this task because of the height of the formaldehyde tank 

openings. These employees had to stand on stools to reach the tank opening. Even though 

employees had gauntlet length outer gloves, we observed that the formaldehyde solution 

flowed between the employees’ outer and inner gloves as they reached into and placed 

the egg ring spindles into the tanks. We also observed employees manually squeezing the 

formaldehyde from the rings with gloved hands to speed up the spindle drying process.

ACGIH considers formaldehyde to be a sensitizer from dermal contact or inhalation 

exposure. To reduce the risk of skin or respiratory tract sensitization, dermatitis, eye or lung 

irritation, and cancer, engineering controls and stringent work practices should be employed 

to reduce dermal exposure and keep air contaminant levels as low as possible. 

Employees involved in the egg preparation process wore North Safety half-mask air 

purifying respirators with filter cartridges approved for formaldehyde or combination 

multicontaminant/P100 respirator cartridges. Employees wore normal length natural rubber 

latex gloves underneath gauntlet style nitrile gloves, safety glasses, and a lab coat. The wallmounted emergency eyewash bottle in the egg preparation area was upgraded to a plumbed 

eyewash station shortly before our May 2010 site visit. 

Inhalable Particulate Matter and Scanning Electron 

Microscopy

Results of personal air sampling for inhalable particulate matter and scanning electron 

microscope examination of the area air sample filters for the presence of moth scales and 

other insect debris are provided in Table 3. Employees’ exposures to inhalable particulate 

matter were below 1 milligram per cubic meter (mg/m3) in many work areas. In contrast, 

substantially higher exposures occurred during moth pouring, work in the egg production 
Health Hazard Evaluation Report 2010-0001-3295 Page 7

room, and during tray scraping. Airborne particulate concentrations were 10 mg/m3 during 

tray scraping in Room 192, and ranged from 6.9–8.4 mg/m3 during moth pouring. Employees 

did these tasks for about 1.5 to 2 hours during the work shift. Exposures would likely be 

greater if they did these tasks for longer periods. We observed that employees doing tray 

scraping sometimes leaned over the trays and barrel while scraping and therefore positioned 

themselves directly in front of the LEV hood opening. This could increase their inhalation 

exposure and obstruct hood exhaust airflow. We observed that employees sometimes used 

compressed air to clean dust off work surfaces, equipment, their clothing, and PPE. This 

practice can aerosolize dust particles into the employee’s breathing zone. 

Results from scanning electron microscope examination of particles in area air samples 

identified the presence of insect debris, moth scales, and moth diet ingredients. In most 

of these area air samples, insect debris was more abundant than moth scales or moth diet 

ingredients. However, the samples collected in the packaging and shipping room and in 

the tray scraping room contained mostly moth scales. Only a small amount of moth diet 

ingredients was found on the samples analyzed by scanning electron microscopy. The 

analytical laboratory reported finding some insect debris in the two field blanks and a few 

moth diet ingredient particles in one of the field blanks. Although the lab reported fewer 

overall particles in the two field blanks compared to the other samples, the presence of these 

particles indicates possible contamination of the samples during collection. Moth scales and 

other insect debris can be allergens and NIOSH has previously identified employees with 

symptoms of occupational allergies from exposure to allergenic particulates during work with 

insects in research and insect rearing facilities [NIOSH 1983, 1984]. Occupational exposure 

limits (OELs) do not exist for moth scales or other insect debris. However, identification of 

these occupational allergens in air samples and the range of employees’ exposures across 

different work areas show which areas had the highest exposures. 
Page 8 Health Hazard Evaluation Report 2010-0001-3295

Table 3. Time-weighted average personal air sample results for inhalable particulate matter 

(August 2010) and descriptive summary of scanning electron microscopy observations of collected 

particulate from area air samples (May 2010) 

Location Work activities Sample 

duration

(minutes)

Inhalable 

particulate 

concentration

(mg/m3)

Scanning electron 

microscope evaluation of 

particles related to 

bollworms from 

area air samples*

North side (clean side)

Room 159 Working in insect diet 

weight room 

(weighing in kitchen for 

92 minutes in morning)

348 0.72 Insect debris, some moth 

scales, small amount of 

moth diet ingredients

Room 160 Working in kitchen 350 0.98 Insect debris, a few moth 

scales, small amount of 

moth diet ingredients

Room 154 – 

Hexcel 

stripping

Handling buckets 

of pupae

412 0.57 Area air sample for 

scanning electron 

microscopy not collected At stripping hood 413 0.96

At stripping hood 250 0.36

Room 147 – 

south cutout

Washing floors, cleaning 405 0.44 Only insect debris 

Washing floors, cleaning was found 402 0.48

Room 301 – 

north cutout

Cleaning, then outdoors 

for 60–90 minutes

300 0.78 Only insect debris 

was found

South side (dirty side)

Moth 

collection 

coolers

Moth pouring 124 8.4 Sample from cooler B – 

Insect debris, a few moth 

scales, small amount of 

moth diet ingredients†

Moth pouring 124 6.9

Dropping 52 2.9

Rooms 196 

and 302 – 

moth 

collection

Cleaning coolers 

and rooms

65 0.47 Sample from cooler B – 

Insect debris, a few moth 

scales, small amount of 

moth diet ingredient†

63 0.56

Egg 

production

Working in egg production room382 0.24 Only insect debris 

was found 397 0.50

329 5.2

Rooms 178 

and 179

Working in 

moth packaging and 

shipping rooms

234 0.60 Mostly moth scales, small 

amount insect debris

Room 181 Irradiation room 

activities

262 0.14 Area air sample for 

scanning electron 

microscopy not collected

Room 192 Tray scraping 84 10 Mostly moth scales, 

some insect debris

*Some insect debris was found on both field blanks.

†Note: A bulk sample obtained from work station within a cooler contained mostly moth scales with 

a small amount of insect debris.
Health Hazard Evaluation Report 2010-0001-3295 Page 9

Carbon Dioxide Measurements

CO2 is a metabolic waste product generated by the newly hatched moth larvae, but is also 

generated by exhaled breath of workers. Spot check measurements for CO2 in the cut-out room 

by FOH industrial hygienists’in June 2008 indicated that levels in the north side of the cut out 

room were 4,109 ppm and were 3,554 ppm in the south side of the cut out room. To help 

decrease CO2 levels, the agency added two exhaust fans in the exterior walls of the cut out 

room, which increased the dilution ventilation from one air change per hour to slightly more 

than two air changes per hour. Follow-up spot checks of CO2 levels by FOH industrial 

hygienists’in September 2009 indicated that levels had decreased to approximately 2,400 ppm. 

Our spot check measurements for CO2 during the May 2010 site visit showed that levels 

in the cutout room were 1,570 ppm in the south side of the cut out room and 1,600 ppm in 

the north side of the cut out room. Additional spot check measurements during our August 

2010 site visit showed that that CO2 levels were 1,260 ppm in the south side of the cut-out 

room and 2,250 ppm in the north side of the cut out room. These levels were well below the 

NIOSH and ACGIH short-term exposure limits of 30,000 ppm; however, periodic 

monitoring to ensure that CO2 levels are maintained well below exposure limits is prudent. 

Heating, Ventilation, and Air-Conditioning System

Heating, ventilation, and air-conditioning (HVAC) was provided throughout the facility by 

ceiling-mounted fan-coil units that provided 500 cubic feet per minute of airflow per unit. A 

maintenance employee told us that the system was designed to provide the majority of the 

facility with approximately 10% outside air. HVAC units were fitted with 1-inch pleated air 

filters rated at 89% efficiency. Dark rooms and cutout rooms on the clean side were supplied 

with 100% outdoor air to control heat, odors, and CO2 generated by developing moth larvae. 

The moth collection and egg production rooms on the dirty side of the facility were 

reportedly maintained under negative pressure to help prevent release of moth scales to 

the clean side via the adjacent corridor. This corridor was separated from the clean side by 

an air curtain and two pairs of swinging doors in series. Moth scales exhausted from moth 

collection and egg production passed through fabric filtration units (bag houses) that were 

reportedly fitted with 99% efficient filtration fabric. Moth scales and other particulates in 

the eight bag houses dropped into 55-gallon drums. The drums were typically about 30% 

full after a week of production. A maintenance person wearing an N95 filtering facepiece 

respirator and lab coat emptied the drums each week by mixing the contents with a water and 

soap mixture and disposing down the waste drain.

Local Exhaust Ventilation Measurements and 

Observations

Insect Diet Weight Room

During production of batched moth diet mixtures, employees manually poured diet 

ingredients from bags into a large garbage container. Personal sampling indicated that 
Page 10 Health Hazard Evaluation Report 2010-0001-3295

exposures to airborne particulates were relatively low; however, we observed that dust was 

generated when employees poured the insect diet ingredients. The garbage container sat on 

a scale and was positioned underneath a flanged rectangular LEV hood that was angled over 

the container (Figure 2). The hood had face dimensions of 22 inches by 17.5 inches and it 

was attached to a 7.5-inch diameter duct that exhausted into an exterior bag house. The top 

of the garbage container was 10.5 to 26 inches from the face of the hood. The average face 

velocity of the hood was 222 feet per minute (fpm). The estimated capture velocity at the top 

of the garbage container was 16–77 fpm. This was below the ACGIH recommended capture 

velocity of 100–200 fpm for contaminants released at low velocity into moderately still air 

[ACGIH 2016]. 

Figure 2. Scale and LEV hood for insect diet ingredient preparation. Photo by NIOSH.

Kitchen

Employees poured ingredients onto a mixing auger equipped with a partially enclosed LEV 

hood. The hood opening was 32 inches by 18 inches and was connected to a 5-inch diameter 

flexible duct, which exhausted into an exterior bag house. The capture velocity at the face 

of the hood where employees poured ingredients was 100 fpm, which meets the minimum 

ACGIH capture velocity recommendations [ACGIH 2016]. Employees’ exposures to 

airborne particulates in the kitchen were low, but we observed airborne dust when batched 

diet ingredients were poured and mixed with bulk wheat germ and soy flour. Additionally, 

airborne dust was generated when employees rolled and shook the container-liner bags to 

empty them after pouring. 
Health Hazard Evaluation Report 2010-0001-3295 Page 11

Hexcel Stripping

Employees removed implanted pupae from Hexcel sheets (rigid polymer small honeycomb 

cell sheets made by Hexcel Corporation) by striking the sheets together in the center of a 

work booth, or by striking the sheets against the bottom surface of the booth. The Hexcel 

stripping area included two work booths. Each booth was 57 inches wide and had side and 

back walls that were 30 inches tall. Each work booth was also fitted with two LEV canopies 

across the top (Figure 3). The LEV hoods exhausted into a bag house outside the facility. 

The capture velocity across the front of the booths was 260–280 fpm. Employees’ exposures 

to airborne particulates were low, but we observed airborne dust during this procedure. 

Additionally, we observed that some employees leaned into the hood while performing this 

task, which could interfere with airflow in the hood and could potentially increase their 

airborne dust exposures. Employees wore long-sleeve lab coats, hair coverings, gloves, and 

N95 filtering facepiece respirators during Hexcel stripping.

Figure 3. An employee standing at the face of the work booth performing the Hexcel stripping 

operation in the booth. Photo by NIOSH.

Moth Collection

Employees had relatively high exposures to inhalable particulates during moth pouring, 

ranging from 6.9–8.4 mg/m3. Employees wore N95 filtering facepiece respirators when 

working in this area. Airborne dust, primarily from insect debris, appeared to be the 

highest as moths were poured from metal trays into cylindrical containers. During pouring, 

employees held a flexible duct as close as possible to capture insect debris (Figure 4). 

However, we observed that a substantial portion of the airborne insect debris was not 

captured by the duct and therefore spread into the employees’ breathing zone. We also 

observed that insect debris contaminated employees’ clothing. The 2.25-inch diameter 
Page 12 Health Hazard Evaluation Report 2010-0001-3295

flexible duct had a capture velocity (measured 2.25 inches from the center of the duct face) 

of 230 fpm in coolers A/B in the 1X collection room and 330 fpm in coolers C/D in the 2X 

collection room. The facility manager said that exhausting larger volumes of air from the 

coolers for the duration of this process was not feasible because the loss of cold air would 

cause temperatures in the coolers to rise and cause the adult moths to become too active. 

Adding a flange to the duct would increase capture velocity, but would not increase overall 

volumetric exhaust.

Figure 4. An employee pouring moths into a small cylindrical container. Photo by NIOSH.

Moth Packing and Shipping

Employees’ exposures to airborne particulates in this area were very low; however, we 

observed that airborne particulates were generated during transfer of moths from the cylindrical 

canisters into metal shipping magazines in the packing room. Employees wore N95 filtering 

facepiece respirators when emptying moth canisters. An LEV hood measuring 21 inches by 

17 inches was angled over the shipping container (Figure 5). The capture velocity 12 inches 

from the face of the hood, where employees transferred moths, was 130 to 240 fpm. 
Health Hazard Evaluation Report 2010-0001-3295 Page 13

Figure 5. An employee manually dumping irradiated moths from cylindrical containers into the 

shipping crate. Photo by NIOSH.

Tray Scraping

Employees scraped debris from moth trays into a plastic barrel that was placed approximately 

12 inches beneath an LEV duct measuring 7 inches in diameter (Figure 6). In addition, a 

large fan was often used to blow airborne particulates away from the tray scraping barrel; 

however, use of this fan decreased the already limited effectiveness of this small LEV duct. 

We observed considerable amounts of airborne particulate when employees were scraping 

moth trays. Personal air samples collected during tray scraping revealed high particulate 

concentrations of 10 mg/m3, indicating that the exhaust ventilation was ineffective. 

Employees wore N95 filtering facepiece respirators in this area. During our evaluation in 

November 2009, the capture velocity 12 inches from the duct opening was 40–60 fpm, which 

was below the ACGIH recommendation of 100–200 fpm [ACGIH 2016]. Following that site 

visit, a rectangular tapered hood with face dimensions of 36 inches by 24 inches was 

installed. The hood was positioned at an angle from the back of the drum, similar to the hood 

placement in the insect diet weight room. The top of the plastic barrel was 9 inches to 

30 inches from the face of the hood. The capture velocity for the new hood was 40–100 fpm, 

at 12 inches from the face of the hood, which was still less than recommended. 
Page 14 Health Hazard Evaluation Report 2010-0001-3295

Figure 6. Tray scraping operation area prior to installation of the LEV hood. Photo by NIOSH.

Respirator Use Observations

During our site visits we observed some instances of improper respirator use. Employees 

wearing half-mask respirators for formaldehyde while working in the egg preparation area 

indicated that they did not regularly inspect the respirators or change their respirator cartridges. 

They also stated that respirators were stored on a table in the egg ring drying room. We 

observed that an employee wearing an N95 filtering facepiece respirator wore both straps over 

the top of earmuff cups. We also observed that some employees had cut off one of the two 

straps of the filtering facepiece respirator. To ensure proper respirator fit, both straps of the 

respirator must be used. In addition, the straps must be positioned directly against the head and 

neck, with one strap over the crown of the head and one strap around the base of the neck. 

Medical Evaluation 

We held confidential voluntary medical interviews with 17 of 19 full-time employees during 

the November 2009 site visit. Employee job titles included moth irradiation, maintenance/

environmental control, moth production and collection, Hexcel stripping, cutout room, egg 

production, egg preparation, kitchen, and egg infestation. Many employees held numerous 

jobs over the years and rotated to different jobs as needed during the production season. Nine 

employees were female and eight were male. Length of employment at the facility ranged 

from 1–41 years with an average of 16 years. 

Five employees reported respiratory irritation or wheezing. Of these employees, three stated 

they had been told by a doctor that they had asthma and were prescribed albuterol inhalers, 

but no diagnostic testing had been done. All three reported their symptoms began while 

working at the facility, and improved when away from work or when working in parts of the 

facility with less exposure to moth scales and insect debris. Seven employees reported skin 

irritation and rash, primarily on their hands and arms. They believed that the dermatitis was 

associated with insect exposure in the cutout room and Hexcel stripping, bleach exposure in 
Health Hazard Evaluation Report 2010-0001-3295 Page 15

Hexcel cleaning, and formaldehyde exposure in egg preparation. A few employees expressed 

concern that there was confusion about what types of PPE were “advised” and what was 

“mandatory” in all production areas, especially during the production season among seasonal 

employees. The employer agreed to post this information in each work area in English and 

Spanish during our November 2009 closing meeting; we verified this was done during our 

May 2010 visit. 

Questionnaires 

A total of 37 employees completed the medical questionnaire in English, and 11 completed the 

questionnaire in Spanish. Below we report questionnaire findings by language because we were 

interested in knowing if there were differences in symptom prevalence or reporting between 

these groups. The average length of employment for those completing the questionnaire in 

English was 9.3 years (range: 1 month to 40 years); the average length of employment for 

those completing the questionnaire in Spanish was 2.4 years (range: one week to 4 years). 

Participants worked in all areas of the facility, with many reporting routinely working in 

multiple areas as needed, especially during the summer production season. 

Table 4 shows the prevalence of symptoms of irritation and/or allergy reported by 

participants to occur regularly after their work shift. Symptom reporting was similar between 

those who completed the questionnaire in English and Spanish. 

Table 4. Symptoms reported by participants to occur regularly 

after their work shift (May 2010)

English (N = 37) Spanish (N = 11)

Itching or tearing eyes 9 (24%) 2 (18%)

Stuffy or runny nose 8 (22%) 3 (27%)

Sneezing 4 (11%) 2 (18%)

Skin rash or hives 6 (16%) 2 (18%)

Table 5 shows reported prevalence of respiratory symptoms and doctor-diagnosed asthma 

and allergy by questionnaire language. Examples of types of reported doctor-diagnosed 

allergies included hay fever and dust, cat, and food allergy. Prevalence of reported respiratory 

symptoms and doctor-diagnosed conditions of asthma and allergy shown in Table 5 were 

higher for those completing the questionnaire in English as compared to Spanish. Table 6 

shows the self-reported smoking status of participants. Of those participants who completed 

the questionnaire in English, 16 of 34 (47%) reported being current or ex-smokers. Of the 

10 participants who completed the questionnaire in Spanish and reported smoking status, 

seven never smoked, and three were ex-smokers (30%).
Page 16 Health Hazard Evaluation Report 2010-0001-3295

Table 5. Symptoms reported by participants by questionnaire language (May 2010)

English (N = 37–40) Spanish (N = 10–11)

Wheezing 7 (19%) 0

Chest tightness/shortness

of breath/difficulty breathing

3 (8%) 0

Awake from sleep with 

cough/chest tightness

4 (11%) 0

Recurrent cough 6 (16%) 1 (10%)

Told by a doctor you have asthma 5 (14%) 0

Told by a doctor you have 

allergies

10 (27%) 0

Table 6. Smoking status reported by participants by 

questionnaire language (May 2010)

English (N = 34) Spanish (N = 10)

Current smoker 11 (32%) 0

Never smoked 21 (62%) 7 (70%)

Ex-smoker 5 (15%) 3 (30%)

In addition to differences in current smoking status, several factors could have contributed to the 

higher reporting of respiratory symptoms between those who completed the questionnaire in 

English as compared to Spanish. Employees who completed the questionnaire in English had on 

average worked at the facility longer (9.3 vs. 2.4 years), so had longer-term exposure to known 

allergens in the workplace. We could not compare symptom prevalence by job title or location 

because during the main production season many employees worked throughout the facility as 

needed. Additionally, there were anecdotal reports from Spanish questionnaire participants of 

concerns about confidentiality and job security; this could have led to underreporting of symptoms.

Spirometry

In May 2010, a prespirometry questionnaire was administered by FOH medical personnel to 

assess whether participants had any medical conditions that prevented their participation, 

such as current flu or bronchitis, middle ear infection, injury, or elevated blood pressure. One 

individual was excluded based on their responses. In May 2010, 46 employees participated 

in FOH administered spirometry. In September 2010, 47 employees participated in FOH 

administered spirometry. Preshift/postshift results were measured for a total of 57 

individuals, with 35 individuals participating in both the May and September testing. A 

preshift/postshift decrease in FEV1 of greater than 10% was seen in 3/57 (5.3%) participants, 

which was considered consistent with lung obstruction. Among these three participants, two 

were current smokers and one was a former smoker; we did not note whether or 

not they had smoked on their day of testing. These three participants had worked at the 

facility for 4–8 years in various job titles. One of these three employees reported sneezing 

and itchy eyes after work as well as cough and wheeze; the other two employees did not 

answer the questions about health symptoms. An additional 8/57 (14%) participants had 
Health Hazard Evaluation Report 2010-0001-3295 Page 17

preshift/postshift decreases of FEV1 of between 5% and 10%; 6 of these 8 participants 

reported respiratory symptoms on their symptom questionnaire. This decrease in FEV1 in 

6 participants who also reported symptoms of cough, chest tightness, or wheezing during 

the shift was considered by both FOH and NIOSH as potential evidence of a work-related 

change in lung function. During the May 2010 spirometry testing, 4/46 (8.7%) participants 

had a FEV1/FVC ratio of ≤ 70%, which is less than optimal in this population. This occurred 

on preshift spirometry for three participants and on postshift spirometry for one participant. 

Information about FEV1/FVC ratios for the September 2010 FOH testing are not available. 

Conclusions

Employees at the PBWRF were exposed to multiple allergens and irritants in many areas 

in the facility. These include formaldehyde, bleach, insects, insect debris, insect diet 

ingredients, and latex gloves. Air sampling results showed that employees were overexposed 

to formaldehyde during egg preparation and disinfection according to NIOSH criteria. In 

addition, employees had dermal exposure and potential for skin sensitization to formaldehyde 

due to the depth of the dipping tanks and formaldehyde solution getting into their outer 

gloves when placing egg rings into the tanks. Inhalable particulate matter containing moth 

scales, insect debris, or insect diet ingredients was not well controlled in the moth pouring, 

egg production, and tray scraping areas indicating that improvements in LEV were needed. 

Medical interviews and questionnaire responses showed that employees were experiencing 

health effects such as eye, respiratory, and skin irritation that were consistent with exposures 

to irritants and allergens. The spirometry results discussed above along with respiratory 

symptoms reported by some employees provided evidence of potential work-related changes 

in lung function; however personal factors such as smoking must also be considered. Once 

someone develops allergic symptoms these symptoms can continue to occur even at very 

low exposures and continued exposure may lead to more severe symptoms. Employees with 

severe allergic symptoms to multiple substances present in the work environment may not be 

able to work in the production parts of the facility. The self-reported symptoms of allergy and 

respiratory irritation are consistent with previous NIOSH reports that identified employees 

with symptoms of occupational allergies during work with insects in research and insect 

rearing facilities [NIOSH 1983, 1984]. 

Recommendations

On the basis of our findings, we recommend the actions listed below. We encourage the 

appropriate managers and employees to use a labor-management health and safety committee 

or working group to discuss our recommendations and develop an action plan on the basis of 

the conditions relevant to the facility today. Those involved in the work can best set priorities 

and assess the feasibility of our recommendations for the specific situation at the PBWRF.

Our recommendations are based on an approach known as the hierarchy of controls 

(Appendix A). This approach groups actions by their likely effectiveness in reducing or 

removing hazards. In most cases, the preferred approach is to eliminate hazardous materials 

or processes and install engineering controls to reduce exposure or shield employees. Until 
Page 18 Health Hazard Evaluation Report 2010-0001-3295

such controls are in place, or if they are not effective or feasible, administrative measures and 

PPE may be needed. 

Elimination and Substitution

Eliminating or substituting hazardous processes or materials reduces hazards and protects 

employees more effectively than other approaches. Prevention through design, considering 

elimination or substitution when designing or developing a project, reduces the need for 

additional controls in the future.

1. Continue research on substitutes for formaldehyde in egg disinfection that are less 

hazardous for employees yet effective as disinfectants. 

2. Eliminate the use of latex gloves. Use nitrile gloves for protection against 

formaldehyde and other dermal hazards. 

Engineering Controls

Engineering controls reduce employees’ exposures by removing the hazard from the process or by 

placing a barrier between the hazard and the employee. Engineering controls protect employees 

effectively without placing primary responsibility of implementation on the employee. 

1. Construct a permanent platform at the formaldehyde disinfection tanks in the egg 

preparation room. To decrease the potential for dermal exposures, platforms should be 

adjustable, but tall enough to ensure that employees do not have to reach up and over 

the formaldehyde tanks. 

2. Install a larger lab hood for egg disinfection so that employees do not need to open the 

hood sash completely to place the spindles into formaldehyde solution. 

3. Use hooks or tongs to lower egg spindles into the formaldehyde containers to limit the 

need to submerge gloved hands and forearms into the formaldehyde solution.

4. Improve the capture velocity of the exhaust hood in the tray scraping area by installing 

a flanged hood and increasing exhaust flow.

5. Consult with a ventilation engineer to modify and improve the LEV for moth pouring. 

Exhaust ventilation systems that filter and recirculate air are commercially available 

and would ensure that the cooled air is not exhausted out of the room. 

Administrative Controls

The term administrative controls refer to employer-dictated work practices and policies 

to reduce or prevent hazardous exposures. Their effectiveness depends on employer 

commitment and employee acceptance. Regular monitoring and reinforcement are necessary 

to ensure that policies and procedures are followed consistently.

1. Instruct employees who disinfect eggs to allow spindles of egg rings to drip dry in the 

hood rather than manually squeezing the formaldehyde. This change will help reduce 

the risk of additional dermal and inhalation exposure. 
Health Hazard Evaluation Report 2010-0001-3295 Page 19

2. Provide and instruct employees to use a vacuum with high efficiency particulate air filters 

instead of using compressed air to clean work surfaces, equipment, clothing, and PPE.

3. Rely on the hooded LEV to remove airborne particulate during the moth tray scraping 

operation. Do not use the large floor fan for additional ventilation as this will diminish 

the effectiveness of the LEV. 

4. Include guidance on filter change out, respirator maintenance, and respirator storage in 

the respiratory protection program. 

5. Educate newly hired employees on workplace exposures, potential health effects, and 

ways to limit exposures such as proper use of equipment, LEV, and PPE. This hazard 

communication education should be repeated for all employees annually at the beginning 

of the main production season in conjunction with respiratory protection training. 

6. Advise employees who have concerns about health symptoms that may be related 

to work such as dermatitis or respiratory irritation to seek medical attention from a 

healthcare provider with experience in occupational medicine. Symptoms should also 

be reported to facility managers. Employees should continue to be evaluated under the 

agency’s medical surveillance program, and referred for further evaluation as needed 

based on their spirometry results. 

Personal Protective Equipment

Personal protective equipment is the least effective means for controlling hazardous 

exposures. Proper use of PPE requires a comprehensive program and a high level of 

employee involvement and commitment. The right PPE must be chosen for each hazard. 

Supporting programs such as training, change-out schedules, and medical assessment may 

be needed. Personal protective equipment should not be the sole method for controlling 

hazardous exposures. Rather, PPE should be used until effective engineering and 

administrative controls are in place.

1. Instruct employees who work in the egg preparation area to regularly inspect 

respirators and change filters following employer guidance. In addition, do not store 

respirators in the work area. After cleaning, respirators should be stored in closable 

containers or bags in a clean area.

2. Require the use of respiratory protection to prevent inhalation and mucous membrane 

contact with airborne allergens in moth collection during moth pouring and during tray 

scraping if the LEV system cannot adequately control employee exposures to moth 

scales or other insect debris. 

3. Eliminate the use of latex gloves. Provide and require the use of nitrile gloves in all 

areas where employees are at risk of dermal exposure to potential allergens. 

4. Give employees working in the egg disinfection area longer cuffed nitrile gloves to 

minimize dermal exposure to formaldehyde. 

5. Ensure that employees consistently wear required PPE for their work area, and 

encourage employees to wear advised PPE. 
Page 20 Health Hazard Evaluation Report 2010-0001-3295

6. Provide employees working in the moth collection rooms with coveralls that are 

laundered on site because of the amount of airborne dust generated during this operation. 
Health Hazard Evaluation Report 2010-0001-3295 Page 21

Appendix A: Occupational Exposure Limits and 

Health Effects

NIOSH investigators refer to mandatory (legally enforceable) and recommended OELs for 

chemical, physical, and biological agents when evaluating workplace hazards. OELs have 

been developed by federal agencies and safety and health organizations to prevent adverse 

health effects from workplace exposures. Generally, OELs suggest levels of exposure that 

most employees may be exposed to for up to 10 hours per day, 40 hours per week, for a 

working lifetime, without experiencing adverse health effects. However, not all employees 

will be protected if their exposures are maintained below these levels. Some may have 

adverse health effects because of individual susceptibility, a pre-existing medical condition, 

or a hypersensitivity (allergy). In addition, some hazardous substances act in combination 

with other exposures, with the general environment, or with medications or personal habits of 

the employee to produce adverse health effects. Most OELs address airborne exposures, but 

some substances can be absorbed directly through the skin and mucous membranes.

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during 

a normal 8- to 10-hour workday. Some chemical substances and physical agents have 

recommended STEL or ceiling values. Unless otherwise noted, the STEL is a 15-minute 

TWA exposure. It should not be exceeded at any time during a workday. The ceiling limit 

should not be exceeded at any time.

In the United States, OELs have been established by federal agencies, professional 

organizations, state and local governments, and other entities. Some OELs are legally 

enforceable limits; others are recommendations. 

● The U.S. Department of Labor OSHA PELs (29 CFR 1910 [general industry]; 29 CFR 

1926 [construction industry]; and 29 CFR 1917 [maritime industry]) are legal limits. 

These limits are enforceable in workplaces covered under the Occupational Safety and 

Health Act of 1970. 

● NIOSH RELs are recommendations based on a critical review of the scientific and 

technical information and the adequacy of methods to identify and control the hazard. 

NIOSH RELs are published in the NIOSH Pocket Guide to Chemical Hazards [NIOSH 

2010]. NIOSH also recommends risk management practices (e.g., engineering controls, 

safe work practices, employee education/training, PPE, and exposure and medical 

monitoring) to minimize the risk of exposure and adverse health effects.

● Another set of OELs commonly used and cited in the United States is the ACGIH 

TLVs. The TLVs are developed by committee members of this professional 

organization from a review of the published, peer-reviewed literature. TLVs are not 

consensus standards. They are considered voluntary exposure guidelines for use by 

industrial hygienists and others trained in this discipline “to assist in the control of 

health hazards” [ACGIH 2017].
Page 22 Health Hazard Evaluation Report 2010-0001-3295

Outside the United States, OELs have been established by various agencies and organizations 

and include legal and recommended limits. The Institut für Arbeitsschutz der Deutschen 

Gesetzlichen Unfallversicherung (Institute for Occupational Safety and Health of the German 

Social Accident Insurance) maintains a database of international OELs from European Union 

member states, Canada (Québec), Japan, Switzerland, and the United States. The database, 

available at 

http://www.dguv.de/ifa/GESTIS/GESTIS-Internationale-Grenzwerte-für-chemischeSubstanzen-limit-values-for-chemical-agents/index-2.jsp, contains international limits for 

more than 2,000 hazardous substances and is updated periodically. 

OSHA requires an employer to furnish employees a place of employment free from 

recognized hazards that cause or are likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. This is 

true in the absence of a specific OEL. It also is important to keep in mind that OELs may not 

reflect current health-based information.

When multiple OELs exist for a substance or agent, NIOSH investigators generally 

encourage employers to use the lowest OEL when making risk assessment and risk 

management decisions. NIOSH investigators also encourage use of the hierarchy of controls 

approach to eliminate or minimize workplace hazards. This includes, in order of preference, 

the use of (1) substitution or elimination of the hazardous agent, (2) engineering controls 

(e.g., LEV, process enclosure, dilution ventilation), (3) administrative controls (e.g., limiting 

time of exposure, employee training, work practice changes, medical surveillance), and 

(4) PPE (e.g., respiratory protection, gloves, eye protection, hearing protection). Control 

banding, a qualitative risk assessment and risk management tool, is a complementary 

approach to protecting employee health. Control banding focuses on how broad categories of 

risk should be managed. Information on control banding is available at 

http://www.cdc.gov/niosh/topics/ctrlbanding/. This approach can be applied in situations 

where OELs have not been established or can be used to supplement existing OELs. 

Formaldehyde 

The International Agency for Research on Cancer classifies formaldehyde as a human 

carcinogen (group 1) on the basis of associations between formaldehyde exposure and 

nasopharyngeal cancer and leukemia [Baan et al. 2009]. NIOSH considers formaldehyde as 

a potential occupational carcinogen, and the U.S. Department of Health and Human Services 

lists formaldehyde as reasonably anticipated to be a human carcinogen in its 14th report on 

carcinogens [NIOSH 1981; NTP 2016].

The OSHA general industry standard for airborne exposure to formaldehyde [29 CFR 

1910.1048] is a PEL of 0.75 ppm for an 8-hour TWA, an action level of 0.5 ppm for an 

8-hour TWA, and a short-term exposure limit of 2 ppm for a 15-minute TWA. These limits 

were established to reduce the risk to workers for cancer; eye, nose, and throat irritation; and 

sensitization. The OSHA standard requires medical surveillance for employees exposed to 

formaldehyde at or above the action level or short-term exposure limit.
Health Hazard Evaluation Report 2010-0001-3295 Page 23

The NIOSH REL for formaldehyde is 0.016 ppm for up to an 8-hour TWA. NIOSH also has 

a 15-minute ceiling limit of 0.1 ppm that is not to be exceeded during a work shift [NIOSH 

2010]. Following the NIOSH carcinogen policy in existence at the time, NIOSH set the REL 

to the “lowest feasible concentration,” which for formaldehyde was defined as the analytical 

limit of quantification of 0.016 ppm for up to 8 hours [NIOSH 1981]. Since then, experience 

has shown that this REL is actually not the “lowest feasible concentration” because 

formaldehyde in the ambient air can exceed 0.016 ppm, a fact NIOSH has acknowledged 

[Lemen 1987]. In addition, NIOSH’s current carcinogen policy acknowledges that, for most 

carcinogens, there is no known safe exposure level. A risk management approach based 

on this premise provides employers with a uniform approach to handling occupational 

carcinogens. NIOSH will continue to recommend reducing exposures to occupational 

carcinogens according to the hierarchy of controls through elimination or substitution and 

implementation of engineering controls, if practical, and the use of administrative controls 

before use of PPE [NIOSH 2016].

ACGIH® does not have an 8-hour TWA, but has a ceiling limit of 0.3 ppm [ACGIH 2017]. 

An ACGIH ceiling limit is an exposure that should not be exceeded at any time during 

the work shift. The ceiling limit is intended to minimize the potential for eye and upper 

respiratory tract irritation. Additionally, ACGIH considers formaldehyde to be a sensitizer 

and a suspected human carcinogen [ACGIH 2001]. 
Page 24 Health Hazard Evaluation Report 2010-0001-3295

Appendix B: Detailed Process Description of 

PBWRF Work Areas

Production Areas

Egg Preparation

Paper rings that had been implanted with insect eggs were collected from the egg 

implantation room, stacked onto spindles, rinsed with a soap and water solution, then rinsed 

with water and allowed to drip dry in small rigid plastic holding tanks (Figure B1).

Figure B1. Spindle of egg rings in plastic holding tanks after being washed with soap and water. 

Photo by NIOSH.

After the initial washing and drying, employees manually immersed the egg ring spindles 

into tanks of dilute (9%) formaldehyde solution for 30 minutes (Figure B2). The employer 

had previously tried dilute sodium hypochlorite and chlorhexidine to disinfect eggs, but 

formaldehyde provided the best disinfection results. The formaldehyde solution tanks were 

located in a laboratory fume hood and were covered during soaking and when not in use. The 

formaldehyde solution in the tanks was reportedly changed every 6 weeks. After soaking in 

formaldehyde, employees removed the egg ring spindles and let the spindles drip dry above 

the formaldehyde tanks for 10 minutes. After drying, the egg rings were rinsed with water 

and cleaned again in a soap and water solution. Employees then placed the egg rings on 

drying racks in the drying area. 
Health Hazard Evaluation Report 2010-0001-3295 Page 25

Figure B2. An employee preparing to submerge a spindle of egg rings into the formaldehyde tank 

located in a lab fume hood. Photo by NIOSH.

Egg Infestation

After disinfection and drying, the egg rings from the insect egg preparation process were cut 

into quarters. Each ring quarter contained 4,500 to 6,000 eggs. The egg ring quarters were 

placed within covered plastic individual larva rearing units that contained a food source for 

hatching larva. This process was referred to as infestation. 

Darkroom

The larva rearing units from the egg infestation stage were placed on maturation carts and 

transferred to a darkroom where they remained for 8 days. The carts were arranged in rows 

so that newly arrived carts were in a single horizontal row at one end of the room, they were 

advanced by one row each day over the next 8 days so that carts of mature larva ended up 

nearest the cutout rooms at the end of the 8-day maturation period. This room had a dedicated 

air handling unit that maintained positive pressure in the room relative to the surrounding 

areas. Because newly hatched moth larvae generated considerable metabolic heat along with 

CO2 and odors, the darkrooms were supplied with 100% outdoor air. Employees entered the 

darkroom daily to advance the maturation carts forward one row toward the cutout room and 

to clean the floors.

Cutout

After the 8-day maturation period in a darkroom, the maturation carts were transferred to a 

cutout room where they remained for 7 additional days while larvae fed on the insect diet in 

the rearing units and continued to mature (Figure B3). Larvae ate their way out of the rearing 

units and dropped onto rectangular Hexcel sheets, positioned beneath the suspended rearing 

units, where they implanted and pupated (Figure B4). The Hexcel sheets were cleaned and 

reused until showing visible signs of wear and tear. Sheets of cardboard were placed under 

each Hexcel sheet and were also reused after being cleaned. Hexcel sheets were changed out 
Page 26 Health Hazard Evaluation Report 2010-0001-3295

by employees 10–12 times over a 7-day period, with six to eight of these changeouts required 

during the 24–48 hours of most rapid growth. During the production season, employees spent 

4–6 hours daily in the cutout rooms. Employees wore N95 filtering facepiece particulate 

respirators. Cutout rooms were also supplied with 100% outdoor air because of CO2

generated by the larva.

Figure B3. Maturation carts with larvae rearing units in cutout room. Photo by NIOSH.

Figure B4. Hexcel sheet where larvae implant and pupate after leaving the rearing unit. Photo by 

NIOSH.
Health Hazard Evaluation Report 2010-0001-3295 Page 27

Some larvae that emerge from the rearing units fail to implant in the Hexcel sheets and 

instead fall to the cutout room floor. Employees use a household leaf blower to blow insect 

larvae bodies and other insect debris to one corner for collection with a high efficiency 

particulate air vacuum. 

Hexcel Stripping

The Hexcel sheets were removed from a cutout room when they were approximately 60% 

implanted with pupae. Employees’ collected pupae from the Hexcel sheets by striking the 

sheets together or against the bottom of the ventilated work booth. The LEV hood exhausted 

into a bag house. Employees wore safety glasses, latex gloves, surgical masks, and lab coats. 

Pupae dropped into a bucket beneath the hood and were weighed and examined. The pupae 

were then placed onto trays and transported to a prep area where they were prepared to either 

go to egg production rooms or moth collection rooms.

Egg Production

Approximately 3% of pupae were hatched into moths in the egg production rooms to provide 

an adequate numbers of eggs to maintain the moth colony from year to year. Egg production 

rooms were maintained at 80 degrees Fahrenheit and 80% relative humidity. After eggs 

were implanted on the specialized egg rings by the moths, they were transferred to the egg 

preparation area for disinfection, as previously discussed. Moth scales and debris were 

exhausted through polyvinyl chloride pipes to scale collectors on the building’s exterior. 

Moth Production and Collection

Another set of rooms was used to hatch pupae for moths destined for irradiation and eventual 

release. Once adult moths emerged from pupae inside cabinets in the moth collection rooms, 

they were transported pneumatically through a sealed system to four large walk-in coolers 

located within these rooms. The colder temperature in the coolers kept the moths in a 

semidormant state to prevent flying and wing damage. In a process called dropping, chilled 

moths were dropped from the sealed transport system into pans and then manually transferred 

into trays for weighing. After the moth trays were weighed, the moths were poured into small 

cylindrical canisters for irradiation and sterilization. Employees manually held a flexible duct 

LEV adjacent to the cylindrical canister during moth pouring to collect airborne particulate. 

Employees were required to wear N95 filtering facepiece respirators, lab coats, and hairnets 

in the moth collection rooms.

Moth Irradiation

An employee irradiated small cylindrical canisters of moths that arrived from the moth 

collection area. Irradiated (sterilized) moths were then transferred to the refrigerated packing 

room via a pass-through cooler. 

Moth Packaging and Shipping

An employee received the small cylindrical canisters of irradiated adult moths through the 

pass-through from the cooler that adjoined the irradiation room and the refrigerated packing 
Page 28 Health Hazard Evaluation Report 2010-0001-3295

room. In the packing room, the employee poured moths from the canisters into a metal 

shipping magazine beneath an LEV hood. Coolant tubes were then inserted into the shipping 

magazine, and the magazine was placed in a shipping box. Each magazine contained 

approximately 2.6 million moths. The boxed magazines were transported by pickup truck and 

air freight to small aircraft that released the moths above cotton fields on the basis of ongoing 

surveillance for naturally occurring bollworm pests. 

Insect Production Support Areas 

Diet Weight Room

One employee weighed and hand mixed powdered ingredients in a 32-gallon garbage 

container that sat beneath an LEV hood. Approximately 24 hours per week were spent 

mixing insect diet ingredients during the production season. The diet was a complex mixture 

of approximately 24 dry and liquid ingredients and included calco red dye. This dye allows 

the irradiated moths that were released to be distinguished from naturally occurring moths in 

cotton fields for surveillance activities. 

Kitchen

An operator put the batched insect diet mixture from the diet weight room into an auger 

along with bulk soy flour and wheat germ. These bulk ingredients came in bags that were 

manually slit and emptied into the LEV-equipped auger. The diet was mixed and cooked in 

the extruder. The diet was cooled and transported by conveyor to the implant room where it 

was put into plastic rearing units with sections of implanted egg rings. 

Hexcel Cleaning

Hexcel sheets used during larva pupation were cleaned and reused. Sodium hypochlorite 

(bleach) (12.5%) was pumped into wash tubs and diluted with water. Hexcel sheets soaked 

for 30 minutes to remove insect debris and then dried. Approximately 2,600 sheets of Hexcel 

and cardboard were used each day during the production season. Hexcel sheets could be 

reused for several years before replacement was required. 

Cardboard Cleaning

Cardboard sheets were passed through an automated cardboard cleaner that brushed off insect 

debris. Managers reported that the cardboard sheets were reused an average of four times 

before replacement. 

Tray Scraping

Moth trays were cleaned and prepared for reuse in the tray scraping room. An employee 

scraped debris from moth trays into a barrel beneath an LEV hood. Employees were required 

to wear coveralls, hairnet, safety glasses, N95 filtering facepiece respirator, and rubber boots 

during this process. Glove use was advised but not mandatory. 
Health Hazard Evaluation Report 2010-0001-3295 Page 29

Appendix C: Tables Table C1. Personal protective equipment requirements, established by the PBWRF Work Area/Duty N95 filtering facepiece Elastomeric half mask respirator Gloves Hairnet Gown Lab coat Hearing protection Safety glasses Apron/ boots Irradiation badge Outside clean-up Bleach tanks A M A Cutout 1x and 2x M Stripping M A A M Cutout leaf blower M M M Cardboard Cleaner M A M M Cardboard Stacking M A Hexcel high pressure 

rinsing

A M

Dark room 1x and 2x MInfest production line M M M MInfest air hose* M MInfest outside Clean-up

M A

Egg prep† M M M M MA = Advised M = Mandatory*All personnel present must wear safety glasses and ear protection while air hose is in use. †Elastomeric half-mask respirators and safety glasses are mandatory during placement and extraction of egg rings from the formaldehyde tanks and rinse tanks. They are no longer mandatory during the process of laying egg rings on dry racks, but are advised.
Page 30 Health Hazard Evaluation Report 2010-0001-3295 Table C1 Continued. Personal protective equipment requirements, established by the PBWRF Work Area/Duty N95 filtering facepiece Elastomeric half mask respirator Gloves Hairnet Gown Lab coat Hearing protection Safety glasses Apron/ boots Irradiation badge QC lab-moth handling and clean-up M Kitchen clean-up M A Kitchen extruder M Cleaning chemicals M A Layers 1x M M A A M A Layers 2x M M A A A A Moth collection drops M A M M A Moth collection vacuum lines M M Moth collection Box/tray cleaning M A M M M Irradiation M Shipping/Packaging M A A M
Health Hazard Evaluation Report 2010-0001-3295 Page 31

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Health Hazard Evaluation Report 2010-0001-3295 Page 33

Keywords: North American Industry Classification System (NAICS) 926140 (Regulation 

of Agricultural Marketing and Commodities), Arizona, Lepidoptera, Pink Bollworm, Insect 

Rearing, Formaldehyde, Inhalable Dust, Dermatitis, Insect Scales, Moth Scales, 

Occupational Asthma
Page 34 Health Hazard Evaluation Report 2010-0001-3295

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Health Hazard Evaluation Report 2010-0001-3295 Page 35

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 U.S.C. § 669(a)

(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).

Disclaimer

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces.

Mention of any company or product in this report does not constitute endorsement by NIOSH.

Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as of 

the publication date.

Acknowledgments

Desktop Publishers: Shawna Watts 

Editor: Ellen Galloway 

Industrial Hygiene Field Assistance: Chad Dowell and Jessica Ramsey 

Logistics: Donnie Booher and Karl Feldmann 

Medical Field Assistance: CDR Jeff McCollum, Indian Health Service, United States Public 

Health Service; Dr. Lee Wugofski and CAPT Erik Vincent, Federal Occupational Health, 

United States Public Health Service

Availability of Report

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

local health department 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 for this report:

NIOSH [2017]. Evaluation of occupational exposures at an insect rearing facility. By 

Gibbins JD, Brueck SE, Sylvain D, Oza A. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH Health Hazard Evaluation Report 2010-0001-

3295, https://www.cdc.gov/niosh/hhe/reports/pdfs/2010-0001-3295.pdf.
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