Sludge Watch ==> Toledo Ohio - Health Study Residents near Sludge Sites

[Maureen Reilly]

Sludgewatch Admin:
For better formatting read the attached PDF file.



Archives of Environmental and Occupational Health
Spring 2007, Vol. 62, No. 1 5


Biosolids result from the treatment of wastewater
(sewage) from municipal, industrial, and commercial
sources. These biosolids can then be used as a soil
conditioner to add organic material to the soil and to improve
growth conditions. In the United States, the majority
of biosolids are applied to farm fields.1
Biosolids can be categorized as either Class A or Class B.
Class A biosolids do not require special handling or other
restrictions because the concentration of pathogens (humandisease–
causing organisms) has been reduced to a very low
level. The pathogens in Class B biosolids have been reduced
in, but not totally eliminated from, the original wastewater.
Four major types of pathogens (bacteria, viruses, protozoa,
and helminths) are generally present in wastewater and
therefore may also be present in Class B biosolids. In addition,
Class A and B biosolids may contain chemicals (including
metals) and allergens, which may be harmful to humans.
1 In the United States, the majority of biosolids used
for land application are Class B.2

The presence of pathogenic microorganisms and toxic
chemicals in biosolids has resulted in an ongoing debate
over the safety of land application. For Class B biosolids to
be applied to an agricultural field, the field must be permitted
by the Environmental Protection Agency (EPA).3 Federal
regulations for the use of Class B biosolids require measures
to restrict public access and to limit livestock grazing
for up to 1 year after land application. However, this restriction
does not apply to occupational access.1

....................

Health Survey of Residents Living
Near Farm Fields Permitted
to Receive Biosolids

Sadik Khuder, PhD; Sheryl A. Milz, PhD; Michael Bisesi, PhD; Robert Vincent, 
PhD;
Wendy McNulty, MS; Kevin Czajkowski, PhD


ABSTRACT. The authors studied the health status of residents living in Wood 
County, OH, near farm
fields that were permitted to receive biosolids. They mailed a health survey 
to 607 households and
received completed surveys from 437 people exposed to biosolids (living on 
or within 1 mile of the
fields where application was permitted) and from 176 people not exposed to 
biosolids (living more
than 1 mile from the fields where application was permitted). The authors 
allowed for up to 6 surveys
per household. Results revealed that some reported health-related symptoms 
were statistically
significantly elevated among the exposed residents, including excessive 
secretion of tears, abdominal
bloating, jaundice, skin ulcer, dehydration, weight loss, and general 
weakness. The frequency of
reported occurrence of bronchitis, upper respiratory infection, and 
giardiasis were also statistically
significantly elevated. The findings suggest an increased risk for certain 
respiratory, gastrointestinal,
and other diseases among residents living near farm fields on which the use 
of biosolids was
permitted. However, further studies are needed to address the limitations 
cited in this study.

KEYWORDS: biosolids, epidemiology, health survey

Archives of Environmental & Occupational Health, Vol. 62, No. 1, 2007
Copyright © 2007 Heldref Publications
Sadik Khuder, Sheryl A. Milz, and Michael Bisesi are with the Department of 
Public Health & Homeland Security at the Health Science
Campus of the University of Toledo, OH. Robert Vincent is with the 
Department of Geology at Bowling Green State University, OH. Wendy
McNulty is with the Health and Human Services System at University of 
Nebraska–Lincoln. Kevin Czajkowski is with the Department of
Geography and Planning at the University of Toledo.

Little is known about the health risk associated with Class B
biosolids for residents living near the fields undergoing
application. These residents are potentially exposed to a
wide variety of agents ranging from heavy metals and other
hazardous materials in industrial waste to bacteria, viruses,
and protozoa in domestic waste.4 Notably, there have been
anecdotal reports of symptoms and disease among communities
surrounding areas where biosolids were applied.5
We examined whether an association existed between
self-reported health effects of residents living in Wood
County, OH, and distance from fields where application of
Class B biosolids was permitted.
METHODS
Wood County has 11 operational wastewater treatment
plants (WWTPs). Plants located in the county’s 2 largest
cities—Bowling Green and Perrysburg—performed the majority
of biosolids application for the county. Biosolids application
may be performed by splash application, injection,
or cake application. The method of application used by each
WWTP is determined independently. At the time of the
study, Bowling Green used splash application and Perrysburg
used cake application. No injection was being performed
in Wood County.
We used a clustered cross-sectional survey design, as approved
by the Institutional Review Board at the University
of Toledo–Health Science Campus. We generated a listing
of all households in Wood County by distance from farm
fields permitted to receive Class B biosolids, using ArcView
software (ArcView 3.2, ESRI, Redlands, CA). To develop
this list, we created a GIS shapefile using input from 3
sources: paper plat maps obtained from the Northwest Ohio
EPA office; a high-resolution aerial, digital orthophoto mosaic
of the county from the Wood County engineer; and a
parcel layer (a map that shows the boundaries of each property)
from the Wood County auditor. We located the fields
where biosolids application was permitted by manually interpreting
photos in the digital orthophoto mosaic. In addition,
we used the plat descriptions from the 2 other inputs to
help locate the permitted fields. We then drew polygons
around each field that had been permitted for Class B
biosolids application. Using ArcGIS software, we produced
a distance buffer zone layer. We calculated and plotted distance
buffer zones from the edges of fields where Class B
biosolids application was permitted for areas by distance
from the nearest field where such application was permitted:
on the field, within 1 mile of the field, greater than 1 mile
and within 2 miles away, greater than 2 miles and within
3 miles away, greater than 3 and within 4 miles away, greater
than 4 and within 5 miles away, and greater than 5 miles
away.6
We selected households on the basis of their distance
from farm fields that were permitted to receive Class B
biosolids. We selected all houses located on these fields
(n  193). From categories developed on the basis of the
house’s distance from the fields, we selected a random sample
of households off the fields. The categories included distances
within 1 mile (1.61 km; n  203) and distances more
than 1 mile (1.61 km; n  211), with this sample divided between
houses within 2 miles (1.61–3.22 km; n  108) and
greater than 2 miles away (3.22 km; n  103). In total, 607
households received the mailed health survey.
The 607 households received mailings that included a
cover letter explaining the study, 1 general household questionnaire,
6 human disease questionnaires, and a postagepaid
return envelope. The first mailing occurred October 3,
2005, with responses requested by October 14, 2005. The
second mailing to nonrespondents was sent October 17,
2005, with responses requested by October 28, 2005. We
sent a third and final mailing to the remaining nonrespondents
on October 31, 2005, with responses requested by
November 11, 2005.
We developed the human disease questionnaire after an
extensive literature review. In addition, we used previously
validated questions from a study of wastewater workers
when appropriate.7 We based the questionnaire on symptoms
and diseases possibly associated with exposure to
agents within biosolids. We included in the questionnaire
demographics (age, sex, race, occupation), smoking habits,
employment in occupations with exposure to infectious
agents (ie, a potentially confounding variable), and the occurrence
of specific physician-diagnosed acute and chronic
diseases and specific self-reported symptoms.
Individuals designated as exposed lived within 1 mile of
a field where application of Class B biosolids was permitted.
Individuals designated as unexposed lived more than 1 mile
from the nearest such field. Therefore, we based the exposure
determination solely on the distance the household was
located from a field where application of biosolids was
permitted.
Data Analysis
For the first analysis, we combined the data for individuals
living on the field with that of individuals living within
1 mile (1.61 km) of the field (exposed group), which we
compared with the data for individuals living more than
1 mile from the field (unexposed group). To accommodate
the clustering of the data at the household level, we used
SAS SURVEY procedures (SURVEYFREQ & SURVEYLOGISTIC8).
To adjust for differences in the number of surveys
received per household, we used survey weights. We
defined the weighting factor as the ratio of the number of individuals
to the number of households for each group.
We compared demographics and other characteristics of
the 2 groups using chi-square analysis. We used logistic regression
models to compare the proportion of individuals
reporting a particular symptom between the 2 areas. We defined
a positive response as an individual symptom reported
to occur during the previous 12 months and a negative
response as no symptom during the previous 12 months. We
6 Archives of Environmental & Occupational Health

tested dose-response relations between frequency of
reported symptom and exposure using the Cochran-
Armitage test.
We performed additional analyses for the exposed group
to determine whether the actual distance of each household
from the farm fields where application of Class B biosolids
was permitted, on the basis of the GIS determination, had a
relationship to the self-reported diseases or symptoms. We
also used logistic regression models in these analyses.
RESULTS
We received 437 surveys from 178 households in the exposed
area and 176 from 80 households in the unexposed
area. The response rate from the exposed households was
50% after 3 mailings for the houses on the fields and 42%
after 2 mailings for houses within 1 mile of the fields. The
response rate from the unexposed households was 36% after
1 mailing for houses more than 1 mile from the fields.
The demographic characteristics of the 2 groups are relatively
similar (see Table 1). The average age for the exposed
area was 41.9 years (SD  23) and for the unexposed area,
41.3 years (SD  23). No significant differences were found
between the 2 groups with regard to gender, race, length of
time living on the farm, percentage of time each year spent
at that address, high-risk occupations, or smoking status.
Table 2 summarizes the symptoms experienced for the previous
12 months for both the exposed group and the unexposed
group. Most of the symptoms experienced occurred
more often among the exposed group than in the unexposed
group. The highest percentage of symptoms, reported among
the exposed group, was for headache, cough, sneezing, and
sore throat. Symptoms significantly elevated in the exposed
group relative to the unexposed group included excessive secretion
of tears (p  .023), abdominal bloating (p  .020),
jaundice (p  .012), skin ulcers (p  .035), dehydration (p 
.009), weight loss (p  .001), and weakness (p  .043). The
Cochran-Armitage test revealed significant dose-response relations
for excessive secretion of tears, abdominal bloating,
and dehydration.
Table 3 summarizes the chronic medical conditions for
both the exposed group and the unexposed group. Emphysema,
arthritis, and chronic bronchitis occurred more frequently
in the exposed group than in the unexposed group,
but the difference was statistically significant for emphysema
only (p  .025). Cases of ulcerative colitis, multiple
sclerosis, Parkinson’s disease, and scleroderma were reported
only among the exposed group. However, these differences
also were not statistically significant.
Table 4 summarizes the frequency of occurrence of acute
disease reported by the exposed group and the unexposed
group. We observed significant elevations in the prevalence
rates of bronchitis (p  .022), pneumonia (p  .045), upper
respiratory infection (p  .023), and giardiasis (p  .023).
Table 5 summarizes results from the logistic regression
analyses for the frequency of occurrence of acute disease
and actual distance from the fields where biosolids application
was permitted. Negative association with distance was
found for bronchitis, pneumonia, upper and lower respiratory
infection, cold, giardiasis, and gastroenteritis. However,
only the association with bronchitis was statistically significant
(p  .042).
Additional analyses of children (aged  18 years) only
revealed no significant differences between the exposed
group and the unexposed group.
COMMENT
We observed an association between respiratory, gastrointestinal,
and general symptoms linked with infectious
diseases and residence in homes near farm fields permitted
to receive Class B biosolids. Moreover, we found a significant
dose-response relationship for excessive secretion of
tears, abdominal bloating, and dehydration. These findings
are in agreement with the findings of Lewis et al9 and studies
on wastewater treatment workers.7 However, they contradict
an earlier study from 3 areas in Ohio, in which researchers
reported no significant differences in the risk of
Spring 2007, Vol. 62, No. 1 7
Table 1.—Demographic Characteristics of the
Study Population
Exposed Unexposed
(n  437) (n  176)
Variable n % n % p
Age (y) .972
 18 95 21.7 40 22.7
18–35 70 16.0 29 16.5
36–59 173 39.6 66 37.5
 60 99 22.7 41 23.3
Gender .630
Male 215 49.9 84 47.7
Female 216 50.1 92 52.3
Race .062
White 409 95.3 174 98.9
Other 20 4.7 2 1.1
Length of time .549
living on farm (y)
 5 147 34.2 57 32.8
510 75 17.4 37 21.2
10 208 48.4 80 46.0
Percentage of time .114
each year living
in the house
50 25 5.8 5 2.9
100 408 94.2 170 97.1
High-risk .726
occupationa
Yes 95 21.7 36 20.5
No 342 78.3 140 79.6
Current smoker .631
Yes 57 13.4 21 11.9
No 369 86.6 155 88.1
aHigh-risk occupations included having been employed in a hospital,
dental clinic, veterinary clinic, long-term care facility, day care
center, wastewater treatment facility, or as a waste collector.

respiratory, gastrointestinal, and general symptoms between
sludge-farm residents and control-farm residents. In the
Ohio study, the biosolids application rates were low and thus
exposure levels may not have been comparable to those in
this study.10
The finding of significantly elevated risk for bronchitis
and upper respiratory infection among residents living near
farm fields where the use of biosolids was permitted agrees
with other published findings. A significantly increased risk
for chronic bronchitis and pneumonia has been reported for
sewage workers,11–14 and possible causative agents include
viruses, other microorganisms, and endotoxins.14–16 Smit
et al17 even reported a dose-response relationship between
endotoxin exposures and flu-like symptoms. Chemical
irritants such as lime, ammonia, and alkyl amines also may
contribute to broncho-obstructive and inflammatory responses.
10 In addition, increased rates of symptoms—including
respiratory problems, eye irritation, nausea, and weakness—
have been reported among residents living near a large-scale
swine farm.18 However, investigators evaluating livestock
waste (which is used as a natural fertilizer) reported that less
than 0.01% of aerosolized microbes are viable,19 possibly indicating
that exposure to aerosolized biosolids is unlikely to
cause infections.
Rates of reported gastrointestinal symptoms, such as abdominal
bloating and giardiasis, were significantly elevated
among the exposed residents in this study. This finding is in
agreement with several studies that have reported that gastrointestinal
symptoms are elevated among sewage workers.
7,14,15,20,21 In addition, Heap and McCulloch22 reported 3
cases of sewage workers who appeared to have become infected
with giardiasis after being exposed to raw sewage
while not wearing personal protective equipment.
The increased risk for ulcer on the skin (and to some
extent, skin rash) among exposed residents is expected.
Lundholm and Rylander23 reported that sewage treatment
plant workers exhibited a higher proportion of skin disorders
than a control group. Residents living near fields where
biosolids are applied potentially are exposed to a wide range
of pollutants, ranging from chemicals such as heavy metals
to various infectious agents, parasites, and noninfectious
bacterial agents. Lewis and Gattie2 suggested that the potential
exists for Staphylococcus aureus to be transmitted from
land-applied biosolids. S. aureus is the suspected agent for a
wide variety of human infections, including skin infections
and pneumonia.24
Newly applied biosolids contain microorganisms. As the
biosolids dry, some microorganisms die and others become
8 Archives of Environmental & Occupational Health
Table 2.—Reported Symptoms for Residents Living
Within 1 Mile of Farm Fields Where Biosolids
Application Was Permitted (Exposed) and Residents
Living  1 Mile From Such Fields (Unexposed)
Exposed Unexposed
(n  437) (n  176)
Symptom n % n % p
Headache 342 80.9 133 76.9 .274
Fever 214 50.4 90 50.6 .615
Excessive 106 25.2 28 16.5 .023
secretion
of tearsa
Cough 346 81.6 133 76.9 .189
Sneezing 351 82.4 139 79.4 .395
Sore throat 310 72.4 118 67.8 .258
Chest pain or 130 30.3 48 27.8 .534
discomfort
Abdominal 180 42.5 64 37.2 .239
pain
Abdominal 150 35.9 44 25.9 .020
bloatinga
Nausea 193 45.8 79 45.9 .985
Vomiting 153 36.3 64 37.4 .789
Diarrhea 273 64.5 111 63.8 .863
Constipation 189 45.1 68 39.8 .236
Jaundice 33 7.9 4 2.3 .012
Skin rash 110 26.1 34 19.8 .105
Ulcer on 36 8.5 6 3.6 .035
the skin
Muscle spasm 128 30.3 44 25.9 .281
Chills 129 30.6 56 32.9 .573
Dehydrationa 72 17.1 15 8.8 .009
Loss of appetite 92 21.8 41 24.0 .565
Weight loss 93 22.1 18 10.6 .001
Insomnia 197 46.6 83 48.5 .664
Fatigue 224 53.2 96 55.5 .612
Weakness 143 34.1 44 25.6 .043
General ill 187 44.8 74 43.0 .686
feeling
Note. Italicized p values are significant at .05.
aSignificant dose-response from the Cochran-Armitage test.
Table 3.—Distribution of Chronic Diseases of
Residents Living Within 1 Mile of Farm Fields
Where Biosolids Application Was Permitted
(Exposed) and Residents Living  1 Mile From
Such Fields (Unexposed)
Exposed Unexposed
(n  437) (n  176)
Disease/condition n % n % p
Asthma 52 12.3 17 9.9 .406
Emphysema 12 2.9 1 0.6 .025
Crohn's disease 1 0.2 1 0.6 .582
Migraine headache 39 9.3 16 9.4 .956
Ulcerative colitis 4 1.0 0 0.0 .099
Chronic bronchitis 26 6.2 5 2.9 .066
Irritable bowel syndrome 30 7.1 16 9.4 .380
Allergies 129 30.5 50 29.2 .762
Multiple sclerosis 5 1.2 0 0.0 .065
Parkinson's disease 4 1.0 0 0.0 .099
Scleroderma 3 0.7 0 0.0 .153
Skin disease 22 5.2 10 5.9 .752
Poliomyelitis 3 0.7 2 1.2 .619
Autism 3 0.7 0 0.0 .153
Skin cancer 9 2.1 4 2.3 .868
Arthritis/osteoarthritis 12 2.8 1 0.6 .057
Note. The italicized p value is significant at .05.

more concentrated along with chemical agents present. The
concentrated form of biosolids may be more irritating after
dermal contact and inhalation.9We found an elevation of excessive
secretion of tears among exposed residents, which
could be explained by the presence of ammonia in the concentrated,
dried biosolids.
Other symptoms significantly elevated in the exposed
group were increased weight loss and general weakness. An
increased risk for central nervous symptoms such as unusual
tiredness has been reported among sewage workers15,17
and among persons in an organic dust environment.25
We observed an increased risk for arthritis and osteoarthritis
in this study. Likewise, Rylander14 reported an
increased risk of joint pain among sewage workers. Thorn
et al26 attributed this increased risk of joint pain to an inflammatory/
systemic response among sewage workers. Possible
causative agents have been reported as viruses such as
Norwalk virus, other microorganisms, and endotoxins.14–16
Cases of ulcerative colitis (3 cases), multiple sclerosis
(5 cases), Parkinson’s disease (4 cases), and scleroderma
(3 cases) were reported in the exposed area. Although no
cases of these diseases were reported in the unexposed area,
the difference between the 2 areas in the number of multiple
sclerosis cases approached statistical significance (p.065).
The lack of statistical significance may be attributed to our
small sample size.
The prevalence of multiple sclerosis (1,171 per 100,000
population) found in this study is significantly elevated
(p  .001) relative to the reported prevalence of 85 per
100,000 for the noninstitutionalized population in the United
States.27 However, a larger sample should be studied to
verify whether the difference is real or just occurred by
chance. A variety of infectious agents have been postulated
as important in the etiology of multiple sclerosis, but a
causal association has not been demonstrated convincingly
for any infectious agent.26–29 An increased risk for multiple
sclerosis is likely to involve a combination of genetic susceptibility
and environmental exposures.30 In addition, a
clustering of multiple sclerosis in Galion, OH, from 1982 to
1985 was attributed to an excess concentration of heavymetal
wastes, especially cadmium and chromium, in sewage
and river water.31 Kraut et al32 reported that neurotoxic effects
can be caused by chemical exposures from sewage.
There are several limitations with this study. First, the results
were based on self-reporting of symptoms and diseases.
It is possible that individuals living near fields where
biosolids are applied and who are exposed to odors and
other biosolids debris may be more prone to report diseases
and symptoms. Odors and other nontoxic emissions from
biosolids could trigger an overreporting of certain symptoms
among residents. In a study in North Carolina, residents
of areas near swine farms reported significantly more
tension, depression, anger, fatigue, and confusion at the time
when odors were present than did a control group of unexposed
persons.33 In addition, retrospective studies indicate
that symptom prevalence near polluted sites can significantly
increase when the ambient air is odorous.34 Finally, irritant
symptoms coupled with a fear of toxicity may produce
a state of autonomic arousal leading to a panic attack. This
panic attack can then progress to a conditioned response in
which subsequent exposure could produce panic attacks
automatically because of a behavioral sensitization to odorants.
35 Unfortunately, we collected no information on odors
in this study.
Spring 2007, Vol. 62, No. 1 9
Table 4.—Distribution of Acute Diseases Among
Residents Living Within 1 Mile of Farm Fields
Where Application of Biosolids Was Permitted
(Exposed) and Residents Living  1 Mile From
Such Fields (Unexposed)
Exposed Unexposed
(n = 437) (n = 176)
Disease/condition n % n % p
Leptospirosis 1 0.2 2 1.1 .281
Salmonellosis 2 0.3 2 1.1 .445
Shigellosis 2 0.3 2 1.1 .445
Typhoid fecer 2 0.3 2 1.1 .445
Hepatitis A 2 0.3 2 1.1 .445
Poliomyelitis 1 0.2 2 1.1 .281
Amoebiasis 1 0.2 2 1.1 .281
Bronchitis 69 16.3 17 9.7 .022
Pneumonia 23 5.5 4 2.3 .045
Upper respiratory 115 27.3 33 18.9 .023
infection
Lower respiratory 25 6.0 6 3.4 .157
infection
Cold 182 43.4 64 36.8 .131
Giardiasis 12 2.9 1 0.6 .023
Gastroenteritis 37 8.8 12 6.9 .415
Note. Italicized p values are significant at .05.
Table 5.—Logistic Regression Results for Acute
Diseases According to Actual Distance From Farm
Fields Where Application of Biosolids Was Permitted
Disease/condition  SE 	2 p
Leptospirosis .84 0.62 1.83 .175
Salmonellosis .45 0.51 0.77 .381
Shigellosis .45 0.51 0.77 .381
Typhoid fever .65 0.52 1.58 .208
Hepatitis A .50 0.51 0.95 .331
Poliomyelitis .84 0.62 1.84 .175
Amoebiasis .84 0.62 1.84 .175
Bronchitis .29 0.15 4.12 .042
Pneumonia .40 0.27 2.28 .131
Upper respiratory .17 0.11 2.25 .134
infection
Lower respiratory .22 0.23 0.92 .337
infection
Cold .09 0.09 0.92 .337
Giardiasis .70 0.47 2.29 .130
Gastroenteritis .12 0.17 0.47 .491
Note. The italicized p value is significant at .05. For the 	2 values:
df  1, n (exposed)  437, n (unexposed)  176.

Second, recall bias is possible, especially with regard to
the frequency of reported symptoms over a long period of
time. We made the assumption that all of the symptoms and
diseases included in the questionnaires are potentially related
to biosolids. However, certain symptoms (such as insomnia
and fatigue) may be related to systemic factors and are
less likely to be related to biosolids. In this study, almost
50% of both the exposed and unexposed groups reported insomnia
and fatigue symptoms, suggesting a nondifferential
recall bias in the exposed group.
Third, the overall response rate for this study was less
than 50%. However, a low response rate is not unusual in
studies conducted in rural areas.36 In addition, despite a
lower response rate for postal questionnaires compared with
interviews, Morgaine et al37 reported that the 2 methods produced
similar health data. Therefore, even with a low response
rate the respondents’ health data are assumed to be
similar to that not collected from nonrespondents. Residents
who are more concerned, have symptoms, or are otherwise
affected by biosolids applications also may be more likely to
respond. We offered a monetary reward to all responding
households in an attempt to minimize this problem. In addition,
the households were not informed of the biosolids
focus of the study (their letter of explanation stated that the
study was on the health status of Wood County residents)
and were also questioned on their knowledge of chemical
fertilizer application, natural fertilizer (animal waste) application,
and biosolids application.
Fourth, residents who responded to the first mailing of the
survey possibly were more or less healthy than those who
responded to the second or third mailings. We did not record
the date of response for any of the returned surveys and
therefore, could not analyze the data to confirm or deny that
such a limitation existed.
Fifth, exposure misclassification is a definite concern with
this study. We classified the exposed group solely on the basis
of the household being located within 1 mile from a field
where biosolids application was permitted. However, exposure
could exist beyond the 1-mile boundary. Moreover, at the
time of the study, we did not know the date of last application,
cumulative amount of biosolids application, direction of the
household from the permitted fields, and meteorological conditions.
We plan additional analyses using the date of last application,
cumulative amount of application, and direction
from the fields once the information has been collected. Researchers
in future studies can evaluate the effect of prevailing
winds on the possible dispersion of biosolids to households
(using the information on the location of the household
and its relative direction from the fields).
Finally, we compared our findings with those in the literature
concerning wastewater workers. However, exposure
characteristics of wastewater workers would presumably
differ from those in residents living near farm fields where
biosolids were applied. For example, potential exposure to
airborne contaminants from wet sewage, more likely to
occur among wastewater workers, is different from the potential
exposure to airborne contaminants from dry
biosolids, more likely to occur among residents living near
farm fields where biosolids were applied, resulting in differing
routes of exposure. In addition, many of the risks to individuals
living near farm fields where biosolids were applied
are chronic and may be evident only after long-term
exposure. Such effects are difficult to measure and relate to
exposure from these fields.
In conclusion, our findings suggest an increased risk for
certain respiratory, gastrointestinal, and other diseases
among residents living near farm fields where the application
of biosolids was permitted. Moreover, the reported
occurrence of certain chronic diseases, such as multiple
sclerosis, were elevated in the exposed group. Further studies
are needed to determine the relation between time from
last application of biosolids and reported health effects as
well as to address cited limitations.
**********
Requests for reprints should be sent to Dr Sheryl Milz, University of
Toledo, DPHHS, 3000 Arlington Ave., Toledo, OH 43614, USA.
E-mail: sheryl.milz at utoledo.edu
**********
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