Guidance for Controlling Potential Risks to

Workers Exposed to Class B Biosolids

This guidance is intended only for controlling health risks to workers from

Class B biosolids during handling and land application. This guidance is not

intended to address nonoccupational exposure.

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

July 2002
SAFER , HEALTHIER , PEOPLE

DISCLAIMER

Mention of any company or product does not constitute

endorsement by NIOSH.

ORDERING INFORMATION

To receive documents or more information about occupational

safety and health topics, contact the National Institute for

Occupational Safety and Health (NIOSH) at

NIOSH—Publications Dissemination

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Telephone: 1–800–35–NIOSH (1–800–356–4674)

Fax: 1–513–533–8573

E-mail: pubstaft@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh

Publication Number 2002–149

This document is in the public domain

and may be freely copied or reprinted.
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Introduction

Biosolids are the organic residues resulting from

the treatment of commercial, industrial, and

municipal wastewater (sewage). One purpose

of the treatment is to significantly reduce the

concentration of disease-causing organisms (also

known as pathogens). Treatment also reduces

the attractiveness of the residues to insects,

birds, and rodents. The product is a material

that can be recycled for uses such as adding

organic material to the soil.

The U.S. Environmental Protection Agency (EPA)

has established two categories of biosolids:

• Class A biosolids have undergone treatment to the point where the concentration

of pathogens is reduced to levels low enough

that no additional restrictions or special handling precautions are required by Federal

regulations [40 CFR* Part 503]. If the Class A

biosolids meet exceptional quality requirements for metals content, they may be

sold in bags and applied in the same way

as other soil conditioners such as peat

moss.

• Class B biosolids have undergone treatment

that has reduced but not eliminated pathogens. By definition, Class B biosolids may

contain pathogens. As a result, Federal regulations for use of Class B biosolids require

additional measures to restrict public access

and to limit livestock grazing for specified

time periods after land application [40 CFR

Part 503]. This allows time for the natural

die-off of pathogens in the soil.

Whereas EPA rules [40 CFR Part 503] restrict

public access to lands treated with Class B

biosolids in order to protect public health, these

rules do not apply to workers involved with

Class B biosolids handling and land application.

*

Code of Federal Regulations.

Workers may come in contact with Class B

biosolids during the course of their work. Workers

and employers may be well aware of the need

for precautions when contacting untreated sewage but less aware of the need for basic precautions when using Class B biosolids. This document provides information, guidance, and recommendations to employers and employees working with Class B biosolids to minimize occupational risks from pathogens. It does not address

other potential safety and health issues such as

injuries or exposures to chemicals.

How are biosolids used?

Biosolids are typically treated to Class B or

Class A standards at the wastewater (sewage)

treatment plant, where a liquid or semi-solid

material is produced. In a liquid state, biosolids

can be transported by truck to a land application site where they are applied directly to

the land using tractors, tank wagons, irrigation

systems, or special application vehicles. Alternatively, biosolids may undergo mechanical

dewatering that may include the use of polymers. Dewatered and liquid biosolids are often

temporarily stored at the treatment plant or

application site. Dewatered biosolids are transported and applied to land using front-end loaders, trucks, tractors, or biosolids-spreading equipment. Most biosolids are applied with spreaders

in semisolid form and then incorporated into the

soil using a disc plow. Workers may come into

either direct or indirect contact with biosolids

during any phase of the treatment, transport, or

application process, or after they are land applied. Currently, more than 50% of the biosolids

generated in the United States is recycled as soil

conditioners to improve and maintain productive

soils and stimulate plant growth rather than being

sent to landfills or incinerated. Biosolids are applied on agricultural land, forestlands, and surface mine reclamation sites. Class A biosolids

are also used in horticultural applications. EPA

estimates that 7.1 million tons of biosolids were

generated for use or disposal in 2000.
What is in biosolids that

requires control of worker

exposures?

There are four major types of human diseasecausing organisms (pathogens) that can be found

in sewage: (1) bacteria, (2) viruses, (3) protozoa,

and (4) helminths (parasitic worms). Class B

biosolids may contain the same types of pathogens as the source sewage, but at reduced concentrations. Both Class A and Class B biosolids

may also contain chemicals (including metals)

and allergens.

To protect public health, the EPA’s 40 CFR

Part 503 rule prescribes a restricted period of

up to 1 year to limit public access to lands

where Class B biosolids have been applied.

These EPA restrictions do not apply to occupational access. EPA does recognize that occupational exposure can occur and states that workers

exposed to Class B biosolids might benefit from

several additional precautions such as use of

dust masks when spreading dry materials, the

use of gloves when touching biosolids, and routine hand washing before eating, drinking, smoking, or using the bathroom.

The risk of worker exposure to infectious agents

in Class B biosolids is likely greatest prior to,

during, and immediately after land application

of the biosolids. Because the concentration of

pathogens declines through natural processes,

the potential for pathogen exposure decreases

over time.

Do we know these

pathogens can cause

disease?

Yes, the association between poor hygiene, raw

sewage, and infectious disease is well established. Most of the pathogenic bacteria, viruses,

and parasites in biosolids are enteric, which

means they are present in the intestinal tracts of

humans and animals. Enteric organisms that may

be found in biosolids include, but are not limited

to, Escherichia coli, Salmonella, Shigella,

Campylobacter, Cryptosporidium, Giardia, Norwalk

virus, and enteroviruses. Exposure may potentially result in disease (e.g., gastroenteritis) or in a

carrier state in which an infection does not clinically manifest itself in the individual but can be

spread to others. These enteric organisms are usually associated with self-limited gastrointestinal

illness but can develop into more serious diseases

in sensitive populations such as immune-compromised individuals, infants, young children, and

especially the elderly.

The disease risk is a function of the number and

types of pathogens in the Class B biosolids relative to the exposure levels and infective dose.

Because data are sparse on what constitutes an

infective dose, it is prudent public health practice to minimize workers’ contact with Class B

biosolids and soil or dusts containing Class B

biosolids during production and application, and

at land application sites during the period when

public access is restricted. Class A biosolids

may also present some health risk to workers,

since some chemicals and biologic constituents

in Class A biosolids are not regulated by the

EPA.

Can workers be exposed to

pathogens from biosolids?

Workers could be exposed to pathogens and irritants when working with Class B biosolids

during the period when public access is restricted. During a NIOSH field investigation at

one biosolids land application and storage site

that did not comply with EPA requirements, the

following was observed:

• NIOSH interviewed employees who worked

in all phases of the biosolids operation. Some

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employees reported repeated episodes of

gastrointestinal illness after working with

the biosolids, either at the treatment plant

or during land application.

• NIOSH observed among workers an inconsistent awareness, provision, and use

of protective equipment and hygiene practices appropriate for handling Class B

biosolids (or biosolids that do not comply

with EPA standards).

• NIOSH collected bulk samples from different locations within the biosolids storage site and found measurable concentrations of fecal coliforms. Fecal coliforms

are used as an indicator for the presence

of other enteric microorganisms. Enteric

bacteria were detected in air samples collected at the land application site.

• The local department of environmental

services recently informed NIOSH that

biosolids applied at this site intermittently

exceeded (by up to 4.5 times) the EPA

fecal coliform upper limit for Class B

biosolids prior to the NIOSH survey.

• The substandard biosolids were applied at

the agricultural site before the monitoring

results were received from the laboratory.

EPA reports that high-pressure spray applications may result in some aerosolization of

pathogens and that application or incorporation of dewatered biosolids may cause very

localized fine particulate/dusty conditions. Also,

farm workers may be exposed to biosolids after

application and during the restricted period. Ancillary workers (for example, laborers hired to

clean trucks that were used to haul biosolids)

can be exposed to biosolids. Exposures to substandard biosolids can occur when these materials are loaded and hauled to approved landfills

or incinerators for disposal.

Additional study of worker exposures to pathogens and other toxics possibly present in

Class B biosolids is needed. This will reduce

scientific uncertainty about these issues and allow further refinement of worker precautions.

What should employers do

to prevent work-related

illness?

To protect workers who have direct contact

with Class B biosolids and thus are likely to

have an exposure to pathogens, employers should

provide a basic level of protection, including

appropriate measures from those listed below.

While the measures are worded to refer to

Class B biosolids, most also apply to tasks involving contact with sewage, untreated or partially treated sludge, or substandard biosolids.

Provide basic hygiene

recommendations for workers.

Basic hygiene precautions are important for

workers handling biosolids. The following list,

originally developed by EPA, provides a good

set of hygiene recommendations.

1. Wash hands thoroughly with soap and

water after contact with biosolids.

2. Avoid touching face, mouth, eyes, nose,

genitalia, or open sores and cuts while

working with biosolids.

3. Wash your hands before you eat, drink,

or smoke and before and after using the

bathroom.

4. Eat in designated areas away from

biosolids-handling activities.

5. Do not smoke or chew tobacco or gum

while working with biosolids.

3
6. Use barriers between skin and surfaces

exposed to biosolids.

7. Remove excess biosolids from footgear

prior to entering a vehicle or a building.

8. Keep wounds covered with clean, dry

bandages.

9. Thoroughly but gently flush eyes with

water if biosolids contact eyes.

10. Change into clean work clothing on a

daily basis and reserve footgear for use at

worksite or during biosolids transport.

11. Do not wear work clothes home or outside the work environment.

12. Use gloves to prevent skin abrasion.

In addition, NIOSH recommends the following steps to provide a more comprehensive set

of precautions for use by employers and

employees:

Provide appropriate protective

equipment, hygiene stations, and

training.

Personal Protective Equipment (PPE).—

Appropriate PPE should be provided for all

workers likely to have exposure to biosolids.

The choices of PPE include goggles, splash-proof

face shields, respirators, liquid-repellent coveralls, and gloves. Face shields should be made

available for all jobs in which there is a potential for exposure to spray or high-pressure leaks,

or aerosolized biosolids during land application. Management and employee representatives

should work together to determine which job

duties are likely to result in this type of exposure, to conduct appropriate on-site monitoring, and to determine which type of PPE is

needed in conjunction with a qualified safety

and health professional. If respirators are needed,

a comprehensive program would include respirator fit-testing and training or retraining.

Hygiene and Sanitation.—Hand-washing stations with clean water and mild soap should

be readily available whenever contact with

biosolids occurs. In the case of workers in the

field, portable sanitation equipment, including

clean water and soap, should be provided. Cabs

should be wiped down and cleaned of residual

mud (or settled dust) frequently to reduce potential for exposure to biosolids.

Training.—Periodic training on standard hygiene practices for biosolids workers should be

conducted by qualified safety and health professionals to cover issues such as the following:

• Frequent and routine hand washing (the

most valuable safeguard in preventing infection by agents present in biosolids), especially before eating or smoking

• The proper use of appropriate PPE, such

as coveralls, boots, gloves, goggles, respirators, and face shields

• The removal of contaminated PPE and the

use of available on-site showers, lockers,

and laundry services

• Proper storage, cleaning, or disposal of

contaminated PPE

• Instructions that work clothes and boots

should not be worn home or outside the

immediate work environment

• Prohibition of eating, drinking, or smoking while working in or around biosolids

• Procedures for controlling exposures to

chemical agents that may be in biosolids

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Reporting.—Workers should be trained to

report potentially work-related illnesses or symptoms to the appropriate supervisory or health

care staff. This may aid in the early detection of

work-relat ed health effects.

Immunizations.—Ensure that all employees

are up-to-date on tetanus-diphtheria immunizations, since employees are at risk of

soil-contaminated injuries. Current CDC recommendations do not support hepatitis A

vaccination for sewage workers.

Extend good environmental

practices to prevent and

minimize occupational

exposures.

• Where feasible, substituting Class A biosolids

could reduce the pathogen exposure risks

during land application compared to applying Class B biosolids. Feasibility may

be affected by local customer preferences, since the two types of biosolids

vary in the nutrient value they provide to

end-users.

• Monitor the source material coming from

the wastewater treatment facility. Check

monitoring results to assure they meet specified Class B or Class A standards prior to

land application operations.

• Monitor stored biosolids prior to application to assure that the biosolids are properly stabilized and that unacceptable

regrowth or cross-contamination from

substandard material has not occurred.

• Where local conditions permit, inject

biosolids below the soil or incorporate

(thoroughly mix) into tilled soil. This will

minimize post-application worker contact

with applied biosolids and prevent

resuspension into the air during periods of

dryness.

• On windy days, avoid spreading or disturbing dry biosolids (e.g., compost) that

would create dust.

• On windy days, avoid spreading biosolids

by high-pressure spray.

• Avoid unnecessary mechanical disturbance

and contact with land-applied Class B

biosolids during the period when public

access is restricted.

• Equip heavy equipment used at storage

and application facilities with sealed,

positive-pressure, air-conditioned cabs that

contain filtered air-recirculation units.

• Monitor worker exposures when adjusting precautions to address site-specific

issues.

For More Information

Additional information about biosolids and

preventive measures can be obtained from the

following government Web sites:

• Environmental Protection Agency (EPA).

Biosolids.

www.epa.gov/owm/bio.htm

(This site includes links to professional

associations that address biosolids.)

• National Center for Infectious Diseases

(NCID). Viral Hepatitis Resource Center.

www.cdc.gov/ncidod/diseases/hepatitis

• National Institute for Occupational Safety

and Health (NIOSH).

www.cdc.gov/niosh

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