Geoscience Reference
In-Depth Information
of biosolids application cannot be validated with adequate scientific knowledge. In
contrast, others opine that the impacts found by field studies are substantial because
the current practice of biosolids application is strictly regulated by federal and state
laws that are based on multiple procedures (Düring and Gath
2002
).
Although biosolids are high in more stable organic content and plant nutrients
and make a good soil amendment, they can also contain metals, organic pollu-
tants, and pathogens. Although processing biosolids attempts to limit the number of
pathogens present, previous studies have shown that pathogenic bacteria often sur-
vive the treatment process (Lewis et al.
2002
; Brooks et al.
2005a
,
b
; Borjesson et al.
2009
). Direct contact of waters contaminated by runoff from nearby land application
sites is one potential mode of human exposure to pathogens present in land-applied
biosolids (USEPA
1999
). Since infection by resistant pathogens poses a unique
treatment challenge, the off-site movement of pathogens, especially those express-
ing antibiotic resistance, is of particular public health importance. With repeated
land application over time, heavy metals can accumulate to levels that may damage
agricultural soils. Arsenic, cadmium, copper, lead, mercury, molybdenum, nickel,
selenium, and zinc can be present in biosolids and are regulated in the Part 503 reg-
ulations. Both pathogens and some heavy metals are known to cause illness (ATSDR
1999
;
2003
;
2004
;
2005
;
2007
;
2008
).
The studies that are most commonly cited are those of STP workers (Brugha et al.
1998
; Weldon et al.
2000
; Trout et al.
2000
; Gregersen et al.
1999
; Rylander et al.
1977
; Lundholm and Rylander
1983
; Elia et al.
1983
; Clark et al.
1984
) and WWTP
workers (Melbostad et al.
1994
; Khuder et al.
1998
). However, there are few studies
on biosolids applicators and residents living in close proximity to biosolids applied
fields.
Varying conclusions are present in epidemiological studies of disease in wastew-
ater workers. Retrospective epidemiological studies have found that wastewater
work presents an increased risk for a variety of symptoms. Melbostad et al. (
1994
)
found in a study of 24 wastewater workers at Norwegian wastewater treatment facil-
ities that workers who were exposed to rod-shaped bacteria reported significantly
higher rates of tiredness after work, headache during work, nausea and respiratory
symptoms. Khuder et al. (
1998
) found in a retrospective epidemiological study of
204 wastewater workers in Ohio that they had a significantly higher prevalence of
gastroenteritis, gastrointestinal symptoms, abdominal pain and headache compared
to workers in other occupations.
In the 2002 NRC report, the information from 14 studies of sewage treatment
plant workers was gathered. Two studies showed that Hepatitis A increased (Brugha
et al.
1998
; Weldon et al.
2000
) while one study showed no increase in Hepatitis
A (Trout et al.
2000
). Additionally, an outbreak of Pontiac Fever, which is caused
by a bacteria transmitted through water, was confirmed (Gregersen et al.
1999
).
Among general complaints were increases in nasal irritation, tiredness, and diar-
rhea which are compatible with exposures to some bacterial endotoxin (Rylander
et al.
1977
). Increased rates of skin disorders, diarrhea, and gastrointestinal symp-
toms have also been reported (Lundholm and Rylander
1983
). A study by Elia
et al. (
1983
) provided evidence of pesticide absorption without reporting any health
