New Occupational Health and Safety Guidelines for Land Applied Sewage Sludges
GUIDANCE FOR CONTROLLING POTENTIAL RISKS TO WORKERS EXPOSED TO CLASS B
BIOSOLIDS
June 12, 2002
Center for Disease Control, Workplace Safety and Health
http://www.cdc.gov/niosh/docs/preprint/pdfs/biosolidsb.pdf
PREPRINT
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. 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.
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. 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 semi-solid 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 fifty percent 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 and forestlands and surface mine reclamation sites, and
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 disease-causing 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 EPA¹s 40 CFR Part 503 rule prescribes a
restricted period of up to one 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 restroom.
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 human 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 where 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 immuno-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 workers¹ contact with Class B
biosolids
and soil or dusts containing Class B biosolids during production and
application, and at land applications 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, which did not comply with EPA requirements, the following was
observed:
NIOSH interviewed employees who worked in all phases of the biosolids
operation.
Some 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 applications 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 sub-standard 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. Exposuresto sub-standard 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 on 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 sub-standard 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, 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.
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)Flush eyes thoroughly, but gently, if biosolids contact eyes.
10)Change into clean work clothing on a daily basis and reserve footgear
for
use at work site or during biosolids transport.
11)Do not wear work clothes home or outside the work environment.
12)Use gloves to prevent skin abrasion.
Additionally, 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-repellant
coveralls,
and gloves. Face shields should be made available for all jobs where
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
health
and safety 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
exposure to biosolids.
Training - Periodic training on standard hygiene practices for biosolids
workers should be conducted by qualified safety and health professionals
that covers issues such as: 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.
Reporting - Workers should be trained to report potentially work-related
illnesses or symptoms to the appropriate supervisory or healthcare
staff.
This may aid in the early detection of work-related 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 re-growth or
cross-contamination from sub-standard 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
re-suspension 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 to limit
aerosolization. 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 governmental websites:
Environmental Protection Agency (EPA): Biosolids. Homepage at:
www.epa.gov/owm/bio.htm (The EPA site includes links to professional
associations that address biosolids.)
National Center for Infectious Diseases (NCID). Viral Hepatitis Resource
Center at: www.cdc.gov/ncidod/diseases/hepatitis
National Institute for Occupational Safety and Health (NIOSH): Homepage
at:
www.cdc.gov/niosh
References
Brugha R, Heptonstall J, Farrington P, Andren S, Perry K, Parry J
[1998].
Risk of hepatitis A infection in sewage workers. Occup Environ Med,
55(8):567-569.
CDC [1999]. Prevention of hepatitis A through active or passive
immunization. MMWR 48(RR-12), Centers for Disease Control and
Protection,
Atlanta, Georgia.
Clark CS [1987]. Health effects associated with wastewater treatment,
disposal, and reuse.
Journal of the Water Pollution Control Federation. 59(6): 436-440.
DeSerres G, Laliberté D [1997]. Hepatitis A among workers from a waste
water
treatment plant during a small community outbreak, Occup Environ Med.
54(1):60-62
Dorn RC, Reddy CS, Lamphere DN, Gaeuman JV, Lanese R [1985]. Municipal
sludge application on Ohio farms: health effects. Environmental Research
38:332-359.
EPA [2002]. Office of Inspector General Status Report: Land Application
of
Biosolids, Environmental Protection Agency, 2002-S-000004, March 28,
2002,
Washington, DC.
EPA [2000]. Guide to Field Storage of Biosolids. Environmental
Protection
Agency, Office of Wastewater Management, EPA/832-B-00-007.
EPA [1999]. Biosolids Generation, Use, and Disposal in the United
States.
Environmental Protection Agency, Office of Solid Waste, EPA530-R-99-009.
Washington, DC.
EPA [1999]. Environmental Regulations and Technology Control of
Pathogens
and Vector Attraction in Sewage Sludge. Environmental Protection Agency,
Office of Research and Development, EPA/625/R-92/013. Washington, DC.
EPA [1995]. Pathogen Risk Assessment Methodology for Municipal Sewage
Sludge
Landfilling and Surface Disposal. Environmental Protection Agency,
Office of
Research and Development, EPA/600/R-95/016. Washington, DC.
Khuder SA, Arthur TA, Bisesi MS, Schaub EA [1998]. Prevalence of
infectious
disease and associated symptoms in wastewater treatment workers. Am J
Ind
Med. 33:571-577.
Kowal NE, Pahren HR [1981]. Health effects associated with wastewater
treatment and disposal. Journal of the Water Pollution Control
Federation.
53(6): 776-786.
Laitinen S, Kangas J, Kotimaa M, Liesivouri J, Martikainen PJ,
Nevalainen A,
Sarantila R, Husman K [1994]. Workers¹ Exposure to Airborne Bacteria and
Endotoxins at Industrial Wastewater Treatment Plants. Am Indust Hyg
Assoc J.
55(11): 1055-1060.
Lodor ML [2001]. Viewpoint: NIOSH Report Omits Significant Details in
LeSourdsville Case.
Biosolids Technical Bulletin, Water Environment Federation. 7(4): 11-13.
Lundholm M, Rylander R [1983]. Work related symptoms among sewage
workers.
Br J Ind Med. 40:325-329.
National Research Council [1996]. Use of Reclaimed Water and Sludge in
Food
Crop Production. National Academy Press, Washington, DC.
NIOSH [1999]. Hazard evaluation and technical assistance report:
Bio-Solids
Land Application Process, LeSourdsville, OH. U.S. Department of Health
and
Human Services, Public Health Service, Centers for Disease Control and
Prevention, National Institute for Occupational Safety and Health, DHHS
(NIOSH) Publication No. 98-0118-2748.
Pillai SD, Widmer KW, Dowd SE, Ricke SC [1996]. Occurrence of Airborne
Bacteria and Pathogen Indicators during Land Application of Sewage
Sludge.
Appl Environ Microbiol 62: 296-299.
Scarlett-Kranz JM, Babish JG, Strickland D, Lisk DJ [1987]. Health among
municipal sewage and water treatment plant workers. Toxicology and
Industrial Health. 3(3):311-319.
Straub TM, Pepper IL, Gerba CP [1993]. Hazards from Pathogenic
Microorganisms in Land-Disposed Sewage Sludge. Reviews of Environmental
Contamination and Toxicology, 132: 55-91.
Thorn J, Kerekes E [2001]. Health Effects Among Employees in Sewage
Treatment Plants: A Literature Survey. Am J Ind Med. 40:170-179.
Trout D, Mueller MS, Venczel L, and Krake A [2000]. Evaluation of
Occupational Transmission of Hepatitis A Virus Among Wastewater Workers.
J
Occup Environ Med 42(1): 83-87.
WEF [1994]. Safety and Health in Wastewater Systems: Manual of Practice
No.
1. Water Environment Federation (WEF), Alexandria, Virginia.
posted by Sludge at 6:15 AM
0 comments
