Mercury

1
Mercury Chlorine ExposuresResidual Effects
4-20 Years After Exposure

• Woodhall Sandy Stopford, MD, MSPH
• Duke University Medical Center

2
Objectives

• List major long-term health concerns from
  excessive occupational exposure to mercury and
  chlorine.
• Identify appropriate studies to evaluate exposure
  to mercury and chlorine.

3
Background

• Chloralkali plant in operation 1956-1994
• Cleanup 1994-1997
• Poor ventilation/repair 1988-1994
• 350 workers total, maximum 150
• Major environmental releases felony convictions
  to owners/management

4
Mercury Exposure Data

• Frequent air data
• Urine data quarterly, QC program since 1988
• Average exposures 2-106 µg/m3
• Maximum air levels 7-147 µg/m3
• Urine levels 13-173 µg/L, average 72
  µg/LCorrected for specific gravity.
  Equivalent to 35 ?g/gm creatinine 25 µg/m3
  exposure

5
Chlorine Exposure Data

• TWA exposures 0.1-0.8 ppm
• Peak exposures 0.01-1.4 ppm
• Exposures at 35 chloralkali plants averaged
  0.006-1.4 ppm
• TLV 0.5 ppm
• STEL 1.0 ppm

6
Group Evaluations

• 1988 NIOSH
• 16 workers. No neurological abnormalities or
  symptoms
• 1988 Duke
• 79 workers high Hg exposures
• No relationship between symptoms and exposure
  measures
• Slight tremors more common in highest exposure
  group

7
NIOSH 1997 Evaluation

• 139 exposed, 107 controls
• Increased symptoms as a group
• Renal function normal
• Reproductive outcomes normal
• No relationship between symptoms and exposure

8
NIOSH 1997 Evaluation

• Visual contrast sensitivity normal
• 8/8 NCV measures normal
• Grip strength normal
• Increased tremor
• Balance normal
• Decreased vibratory sensation

9
NIOSH 1997 Evaluation

• Multivariate exposure-effect analysis
• Overall 5/87 measures worse than expected
• 9/87 better than expected
• For multiple comparisons use cut point of p
  0.002 no significant relationships

10
Case Study

• GB is a 73 year old gentleman who was diagnosed
  as having memory problems, cognitive impairment,
  a gait disorder, impairment of fine motor speed
  and dexterity secondary to mercury exposure.

11
Case Study

• Exposure
• Assistant cell operator from 1963-1966
• Products operator 1966-76
• 1976-87 relief operator in products area and cell
  room
• 1987-93 shift foreman
• Chlorine no medical treatment, respirator when
  ever saw plume

12
Case Study

• Monitoring
• Urine mercury levels 1978-1992 range nd-29,
  average 11 mcg/L
• Pulmonary function normal 1979
• Neurological exams normal 1981-1991

13
Case Study

• Medical History
• Pernicious anemia first noted 1985. Vit.
  B12 treatment stopped 1997
• Low Vit. B12 2001
• Memory problem, mood swings, difficulty with
  balance, numbness and tingling starting 1998 with
  worsening in 2003.

14
Case Study

• .Neuropsychiatric findings
• Deficits in attention and concentration
• Poor visual and recognition memory
• Difficulty with fine motor speed and dexterity
• Positive sleep study with low blood oxygen

15
Case Study

• Exam
• Peripheral sensory neuropathy
• Assessments
• Pernicious anemia
• Obstructive sleep apnea with hypoxemia

16
Case Study

• Recommendations
• Institute treatment for Vit. B12 deficiency
  associated with brain effects
• CPAP for obstructive sleep apnea
• Consider cognitive training for memory defect
• Repeat neuropsychological testing in 1 year

17
Duke 2001 Evaluation

• 80 self-selected ex-workers
• 52 found to have exposure-related problems on
  screening study
• 51/52 had confirmatory assessments

18
Duke 2001 Evaluation

• Mercury-related concerns
• Depression
• Poor concentration/memory
• Personality changes
• Tremor
• Neuropathy
• Constricted visual fields
• Loss of teeth

19
Duke 2001 Evaluation

• Chlorine-related concerns
• Reactive upper airways
• Reactive lower airways
• Aggravation of asthma

20
Duke 2001 Evaluation

• Components of Evaluation
• Occupational and medical history (duplicate of
  1988 evaluation)
• General examination

21
Duke 2001 Evaluation

• Components of Evaluation
• Specialists evaluations
• Neuropsychologists
• Neurologists
• Otolaryngologists
• Peridontists
• Pulmonologists

22
Duke 2001 Evaluation

• Components of Evaluation
• Confirmatory studies
• Neuropsychological testing
• EMG/NCV
• MRI/CT of Brain/EEG
• CT/MRI of sinuses
• Spirometry/lung volumes/diffusion before and
  after bronchodilators or exercise

23
Duke 2001 Evaluation Results

• Memory/Neuropsychological Abnormalities
• 20 of 51 with concerns
• 14/20 not confirmed
• 13/20 depressed
• 2 not evaluated (both pre/post exposure)
• 5/18 tested malingering
• 2 with strokes
• 1 with ADD
• 1 with psychotic depression

24
Duke 2001 Evaluation Results

• Neuropathy
• 18/51 with concerns
• 14/18 not confirmed
• 4/18 not tested, all with symptoms pre/post
  exposure

25
Duke 2001 Evaluation Results

• Tremor
• 11/51 with concerns
• 10/11 not confirmed
• 1 confirmed onset after exposure (caffeine)
• Tooth loss
• 3/51 with concerns
• 3/3 not confirmed (poor dental hygiene/caries)

26
Duke 2001 Evaluation Results

• Chlorine-related Concerns
• RUDS 5/51
• 5/5 evaluated not confirmed
• RADS 14/51
• 8/14 not confirmed
• 2 severe post pneumonia/ rheumatoid arthritis
• 4/14 mild all smokers

27
Duke 2001 Evaluation

• Exposure Correlates
• Mercury high/medium vs low
• Depression (17 cases) OR 1.1
• Carpal tunnel (5 cases) OR 1.2
• Chlorine high/medium vs low
• Airway reactivity (7 cases) OR 0.95

28
Duke 2001 Evaluation

• Conclusions
• Screening studies during high exposures to Hg
  found no consistent effects except increased
  symptoms and more mild tremors in high exposure
  group (NIOSH and Duke)
• NCV studies during high exposure normal
• Screening testing 4-20 years post exposure
  unremarkable

29
Duke 2001 Evaluation

• Conclusions
• Specialty studies 4-20 years post exposure did
  not identify mercury or chlorine-specific effects
  of neuropsychological or pulmonary function
• Clinical screening and removal based on
  biological monitoring appears to be effective in
  preventing long term consequences