Neurotoxicity from Municipal Sewage Sludge


Case Study of Sewage Sludge Exposure:

Purpose

To evaluate the neurobehavioral effects of municipal sewage sludge in a family whose members were exposed for 8 or more years. Municipal sewage sludge, a mixture of household sewage along with industrial waste, is routinely applied as fertilizer to some farms in the USA.

This complex substance poses a significant neurotoxic threat to farmers, their workers, nearby residents, and possibly to the general population through the food supply. Recently, the FDA attempted to allow food grown with such materials to be labeled as "organic", but is now reconsidering due to massive citizen protest. However, such food is still permitted in the general food supply.

In this case, industrial waste in the subject's household water supply included numerous chemicals such as lead (1000 ppb) and manganese (100 ppb) (these values above the maximum concentration levels permitted). Due to the clay under the soil, the drainage flowed towards the subject's property. The family's livelihood, a herd of 150 cattle, deteriorated to the point where they were given up and the property was abandoned.

Method

Neuropsychological testing of 9 family members.

Results

Based on results of the Neurotoxicity Screening Survey, symptoms consistent with neurotoxicity were found in all who completed the test. The two children born and raised on the farm have been classified by their schools as mildly retarded and having attention-deficit disorders, although there was no family history of these illnesses.

Similar results were found in numerous family members. Case 1 will be presented here.

Case 1 was a 56 year old grandmother in prior good health, with a B.A. degree. Estimated pre-morbid FSIQ was 114. Current FSIQ was 98, with specific deficits in immediate memory, arithmetic, visual memory and visuo-spatial organization (scaled scores of 8,7,8,9); visual retention (14 errors); verbal fluency (COWAT of 18); visual figure-ground perception (Embedded Figures Test (5%tile)); learning (Expanded Paired Associate Test (1%tile immediate, 4%tile delayed)); manual dexterity (Grooved Pegboard Test (<1%tile)); attentional skills (PASAT <<1%tile)); executive function ( Stroop <<1%tile), Trails <<5%tile)); Logical memory <<1%tile); Visual Search and Attention Test <<1%tile); with mild anxiety, mild-moderate depression, normal mood; no indication of malingering on several specific tests of this function; and personality testing showing no personality disorders, high levels of conscientiousness and extraversion, low in neuroticism, average in openness and agreeableness. Similar results of cognitive testing were found in other family members.

Sural nerve testing found slowed velocity on the left (33 M/s), and abnormal amplitude and evoked potential dispersion on the right.

Conclusion:

Municipal sewage sludge poses a measurable neurotoxic hazard to nearby residents and farm workers, who need to be informed of possible neurotoxic injury from their exposure, and then monitored using repeated neurobehavioral tests.

Municipal Sewage Sludge : Scope of the Problem

  1. Nearly 1/2 of all the municipal sludge produced in the USA each year -- up to four million metric tons -- is spread on farmland. Several farm and food organizations, including the American Frozen Food Institute, are calling for a halt to the practice of applying sludge to farmland (Haag, 1992).
  2. Although the U.S. EPA has minimal guidelines, local agencies can also issue sludge application permits.
  3. Of 30 municipal sludges analyzed, 90 percent had levels of toxic metals above federal guidelines permitted for sludge.
  4. There are no federal guidelines for the testing of dioxin and a myriad of other highly toxic industrial byproducts currently found in most municipal sludge. Most of the over 60,000 chemicals currently used in U.S. industry eventually find their way into the sewer system and then municipal sludge. These chemicals will interact to form new chemicals, which may be more toxic than the original chemicals (Haag, 1992).
  5. The U.S. EPA promulgated regulations in 1993 that permits sewage sludge that is too contaminated with certain toxic pollutants to be disposed of safely in a landfill to be promoted as a fertilizer safe to apply to crops (National Sludge Alliance, 1997).
  6. When long-term accumulative effects are considered, livestock are particularly vulnerable to subtle degradation of food and water, due to bio-accumulation. Cows may consume soil -- up to 14 percent of dry matter intake -- when available forage is low and no supplemental feed is available (Haag, 1992).
  7. References
    1. Haag, Ed, 1992. Farm Journal, March, pp. 16 -- 19.
    2. National Sludge Alliance, 1997. Public Facts No. 111, April 16

Exposure Analysis

Family years on the property: 26
Activities on the family farm: Dairy production
Number of family members living on the property: 2 great-grandparents, 2 grandparents, 3 adult children, 2 great-grandchildren
Type of pollution: Wetland municipal sewage dump site
Years that the dumping occurred: Last 8 years of residence and milk production
Acres of the dumpsite> 70
Proximity of the family property to the dumpsite: Adjacent
Routes of exposure: Air, water, dust>
Onset of symptoms: One year after dumping began
Systems affected: Mucous, respiratory, nervous
Type of pollution: Household sewage mixed with industrial waste
Use of the pollutant: Fertilizer for public food supply

Specific chemicals found

  1. Toxic levels found at the subject's property: This analysis is incomplete at this time. Possible contaminants include solvents, pesticides, PCB, formaldehyde, etc.
  2. Metals can combine with sewage to form organic metals, more toxic (bio-available) than simple metals.
  3. The actual individual toxic substances would vary from day-to-day, depending upon the industry discharging the waste.
  4. The potential for the presence of neurotoxic substances is large.

Individual Analysis

  1. See Appendix 1. The subject showed signs and symptoms consistent with neurotoxicity from sewage sludge.

Group Analysis

  1. See Appendix 2.
    1. There was a significant decline in observed versus predicted cognitive function as measured by WAIS-R FSIQ.
    2. There was a significant difference between Vocabulary and Digit Symbol subscale scores (resistant versus susceptible cognitive functions)
    3. Significant symptoms of neurotoxicity were reported by family members.
    4. Distortion was within normal limits.
    5. No malingering was found.

Appendix 1: Case Data

Test Date: 1997
Gender: Female
Age: 56
Educational Level: 16 years, B.A.
Marital Status: Married
Ethnicity: White
Number of Children: 7

(Note: WNL means within normal limits for the individual.)

Premorbid IQ Estimates:

Based on a demographic formula (Reference: Vanderploeg, R. & Schinka, J. (1995). Predicting WAIS-R Premorbid Ability: Combining Subtest Performance and Demographic Variable Predictors. Archives of Clinical Neuropsychology, 10(3), 230 & 232) which considers education, occupation, and vocabulary, expected premorbid IQ would be approximately:

  Score Percentile
Full Scale 114 82%

In January 3, 1992, the subject's reading vocabulary was in 97th percentile (compared with high school seniors). This result suggests a higher IQ than her occupational history would reflect. (Occupation is used to determine the pre-morbid IQ in the above equation). However, the demographic equation results comparison score will be used provisionally.

Cognitive Testing Standard: Scores significantly below the standard are considered abnormal for the subject and deficit.

 
Overall IQ
Percent
Scaled Score
Equiv.
Cutoff
Scaled/Percentile
Full Scale
114
82
13
9/37

Wechsler Adult Intelligence Scale, Revised: WAIS-R

 
Age - Adjusted Scaled Scores Percentile
Classification
   
Verbal Subscales        
 

Information

10
50%
   
  Digit Span
8
25%
*  
  Vocabulary
14
91%
   
  Arithmetic
7
16%
*  
  Comprehension
14
91%
   
  Similarities
11
63%
   
 
Performance Subscales        
 

Picture Completion

8
25%
*  
  Picture Arrangement
11
63%
   
  Block Design
9
37%
*  
  Object Assemblyn
10
50%
   
  Digit Symbol
11
63%
   
 
Verbal IQ:
103
58%
Average  
Performance IQ:
95
37%
Average *
Full Scale IQ:
98
45%
Average *

Interpretation: An overall decline in IQ was found, with specific deficits in immediate memory, arithmetic, visual memory and visuo-spatial organization.

Benton Visual Retention Test (Administration B, Form C). This test assesses the ability to remember, based upon visual input. Comparison IQ = 114

 
Expected for IQ
Observed
Difference
Number correct
7-1=6
2
4
Number errors
4+2=6
14
8

Interpretation:

Number correct score: Strong indication of acquired impairment of cognitive function

Number of errors score: Strong indication of acquired impairment of cognitive function

Controlled Oral Word Association Test evaluates verbal fluency, the ability to find and use words.

Total number: 17 - 7 = 10 Percentile: 1%
Interpretation: Deficit    

Embedded Figures Test evaluates the ability to detect visual figure-ground relationships (the use of the eyes to make sense out of what the eye sees).

Number detected out of 40 objects: 20
Percentile for age and education: 5%
Interpretation: Deficit

Expanded Paired Associate Test evaluates ability to learn pairs of words (verbal learning ability). (Norms based on age; gender and education not correlated.)

 
Immediate Recall
Delayed Recall
Score
9
4
Percentile
<1%
4%
Interpretation
Deficit
Deficit

Grooved Pegboard Test evaluates manual dexterity (the ability to use hands in a sensitive and productive way).

Dominant Hand: Right
Dominant
Non-dominant
Time for completion:
175"
197"
Percentile:
<1%
<1%
Interpretation
Deficit
Deficit

Neurotoxicity Screening Survey:

Factor
Results
 
Score
Classification
Memory and Concentration
91
Elevated
Autonomic Nervous System
88
Elevated
Vision
22
Elevated
Hearing
9
Elevated
Balance
4
Elevated
Smell-Taste
7
Elevated
Peripheral Numbness
21
Elevated
Sensory-Motor
72
Elevated
Chemical Sensitivity
10
Elevated
Emotionality
47
Elevated
Distortion I
15
WNL
Distortion II
10
WNL
     
Overall Neurotoxicity Indicator
371
Elevated

Interpretation: Symptoms consistent with patients with neurotoxicity.

Paced Auditory Serial Addition Test evaluates auditory information processing and tracking.

Number correct of 60: 23 Percentile: 0.7

Interpretation: Deficit

Stroop Color and Word Test evaluates mental flexibility (45 sec administration).

 
Number
T-Score
Percentile
Interpretation
Word reading:
57
24
<1%
Deficit
Color naming:
24
<20
<1%
Deficit
Color/Word:
18
23
<1%
Deficit

Trailmaking Test evaluates visuomotor tracking (the ability to search and locate with the eyes) and attention (the ability to concentrate on a task so learning and other mental functions can take place). (Norms based on gender, age and education.)

 
Part A
Part B
Time for completion:
60"
122"
Scaled score:
5
6
Percentile:
3.5%
5%
Interpretation:
Deficit
Deficit

Wechsler Memory Scale: Logical Memory evaluates the ability to remember a chain of logically related cognitive elements, like a simple story. (Norms based on IQ and age).

Estimated verbal IQ: 114

 
Immediate recall
Delayed recall
Number expected:
27
16
Number observed:
19
11
Probability of normality:
0.0005
0.019
Interpretation:
Deficit
Deficit

Visual Search and Attention Test

 
Left
Right
Total
Score
24
18
42
Percentile
1%
1%
1%
Interpretation
Deficit
Deficit
Deficit

EMOTIONAL FUNCTION

Beck Anxiety Inventory measures emotional anxiety.

Score: 12.

Interpretation: Mild anxiety

Beck Depression Inventory measures emotional depression.

Score: 16.

Interpretation: Mild-moderate depression

Profile of Mood States

 
Raw Score
T Score
%
Tension
6
33
4%
Depression
4
35
7%
Anger/Hostility
11
47
40%
Vigor
18
64
92%
Fatigue
17
55
70%
Confusion/Bewilderment
13
49
45%

Interpretation: Low levels of tension and depression.

WELL-BEING MEASURES

General Well Being Schedule evaluates general well-being compared with the population of the US.

Score: 58
0-60 Severe Distress
61-72 Moderate Distress
73-110 Positive Well-being

Human Activity Profile measures levels of physical activity.

  Score Percentile
Maximum Activity Score 62 <1%
Adjusted Activity Score 57 <1%
Activity Age 70+  

Interpretation: Deficit

DISTORTION AND MALINGERING TESTS

Endorsement of Rare Symptoms. The Neurotoxicity Screening Survey presents 14 symptoms that are rare. If a number of these symptoms are endorsed, the question of distortion is highlighted.

 
Number endorsed:
Distortion I:
4
Distortion II:
1

Interpretation: A low level of distortion was present.

Memorization of "16" Items (Iverson & Franzen, 1991) requires the subject to memorize a list of 16 items. Because the 16 items are grouped into four conceptual categories, the task is easier than it looks. A cutoff of 6 is used to suggest malingering.

Number correct: 12

Interpretation: Non-malingering

Portland Digit Recognition Test, a memory recognition test, requires the subject to memorize a 5 digit number and recognize the same number when given two choices of 5 digit numbers. By chance alone, the subject should respond correctly 50% of the time.

Percent correct responses (5 sec delay): 3/3
Percent correct responses (15 sec delay): 3/3
Percent correct responses (30 sec delay): 2/2

Interpretation: Within normal limits

Twenty-one Item Memory Test assesses the probability of malingering based on a forced choice comparison (Iverson and Franzen, 1989). If the subject does not remember correctly nine of the 21 items on the forced choice test, the subject may be malingering.

Number of words correctly recalled:

Free recall: 7
Forced choice 13

Interpretation: Non-malingering

Appendix 2: Group Analysis

Predicted IQ v Observed IQ

Number of subjects: 8

 
Mean
Standard Deviation
Age:
41
16
IQ (Percentiles):    
- Predicted:
66
22
Observed:
23
15

Prob. of normal t-value, 1 tailed test = < .0001

Vocabulary minus Digit Symbol

Number of subjects: 6

 
Mean
Standard Deviation
Vocabulary (percentiles)
66
25
Digit Symbol
23
20

Prob. of normal t-value, 1 tailed test = < .0003

Neurotoxicity Screening Survey Results

Number of subjects: 5
Number with positive scores: 5
Number with positive distortion: 0

Malingering Test Results

Number of subjects: 6
Number of tests administered: 17
Number with positive malingering: 0

Sural Nerve Conduction Velocity Results

Number of Subjects: 6
Number of nerves tested: 12
Number with slowed nerves: 10

Immune Testing

Number of subjects: 6
 
Number of tests positive for exposure to:  
- Formaldehyde: 4
  TMA: 3
  Isocyanate: 1
 
Number of tests positive for auto-immunity to:  
  Stomach: 3
  Small intestine: 4
  Kidney: 3
  Liver: 2
  Nuclei: 3
  Myelin: 5
 
Number of tests showing:  
  Abnormal TA-1: 3
  Elevated IL-1: 2
  Decreased IL-1: 2
Copyright © 1999 Raymond Singer, Ph.D., All rights reserved. No portion of this article may be reproduced without the express written permission of the copyright holder. If you use a quotation, excerpt or paraphrase of this article, except as otherwise authorized in writing by the author of the article you must cite this article as a source for your work and include a link back to the original article from any online materials that incorporate or are derived from the content of this article.

This article was last reviewed or amended on Apr 28, 2015.