California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 7 - General Industry Safety Orders › Group 16 - Control of Hazardous Substances › Article 109 - Hazardous Substances and Processes › Appendix C - Medical Surveillance Guidelines

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
Introduction
The occupational health standard for lead was
						  promulgated to protect workers exposed to lead which, as defined by the
						  standard, includes metallic lead, all inorganic lead compounds and organic lead
						  soaps but excludes all other organic lead compounds. The term "inorganic lead"
						  used throughout this appendix is meant to be synonymous with the definition of
						  lead set forth in the standard.
Under this final standard in effect as of September 8,
						  1979, occupational exposure to inorganic lead is to be limited to 50
						  [MICRO]g/M3 (micrograms per cubic meter) based on an
						  8-hour time-weighted average (TWA). This level of exposure must be achieved
						  through a combination of engineering, work practice, and administrative
						  controls (in periods of time ranging from 1 to 10 years) in primary lead
						  smelting, secondary lead smelting, electronics, gray iron foundries, ink
						  manufacture, paints and coatings manufacture, can manufacture, and printing. In
						  these industries, respirators may be used to meet the 50
						  [MICRO]g/M3 exposure limit pending the
						  implementation of the prescribed controls. For all other industries, there is
						  no prescribed period during which compliance with the PEL must be achieved by
						  controls other than respiratory protection.
The standard also provides for a program of biological
						  monitoring and medical surveillance for all employees exposed to levels of
						  inorganic lead above the action level of 30
						  [MICRO]g/M3 (TWA) for more than 30 days per
						  year.
The purpose of this document is to outline the medical
						  surveillance provisions of the standard for inorganic lead and to provide
						  further information to the physician regarding the examination and evaluation
						  of workers exposed to inorganic lead.
Section I provides a detailed description of the
						  monitoring procedure including the required frequency of blood testing for
						  exposed workers, provisions for medical removal protection (MRP), and
						  notification and recordkeeping requirements of the employer. Discussions of
						  respirator use, respirator monitoring, and chelation therapy are also
						  included.
Section II discusses the toxic effects and clinical
						  manifestations of lead poisoning and effects of lead intoxication on enzymatic
						  pathways in heme synthesis. The adverse effects on both male and female
						  reproductive capacity and on the fetus are also discussed.
Section III outlines the recommended medical evaluation
						  of the worker exposed to inorganic lead including details of the medical
						  history, physical examination, and recommended laboratory tests, which are
						  based on the toxic effects of lead as discussed in Section II.
Section IV provides detailed information concerning the
						  laboratory tests available for the monitoring of exposed workers. Also
						  discussed are the relative value of each test and the limitations and
						  precautions which are necessary in the interpretation of laboratory
						  results.
I. Medical surveillance and monitoring requirements for
						  workers exposed to inorganic lead.
Under the occupational health standard for inorganic
						  lead, a program of biological monitoring and medical surveillance is to be made
						  available to all employees exposed to lead above the action level of 30
						  [MICRO]g/M3 TWA for more than 30 days each year.
						  This program consists of periodic blood sampling and medical evaluation to be
						  performed on a schedule which is defined by previous laboratory results, worker
						  complaints or concerns, and the clinical assessment of the examining
						  physician.
Under this program, the blood lead level of all
						  employees who are exposed to lead above the action level of 30
						  [MICRO]g/M3 is to be determined at least every six
						  months. The frequency is increased to every two months for employees whose last
						  blood lead level was between 40 [MICRO]g/100g whole blood and the level
						  requiring employee medical removal to be discussed below. For employees who are
						  removed from exposure to lead due to an elevated blood lead, a new blood lead
						  level must be measured monthly. A zinc protoporphyrin (ZPP) measurement is
						  required on each occasion that a blood lead level measurement is made.
An annual medical examination and consultation
						  performed under the guidelines discussed in Section III is to be made available
						  to each employee for whom a blood test conducted at any time during the
						  preceding 12 months indicated a blood lead level at or above 40 [MICRO]g/100 g.
						  Also, an examination is to be given to all employees prior to their assignment
						  to an area in which airborne lead concentrations reach or exceed the action
						  level. In addition, a medical examination must be provided as soon as possible
						  after notification by an employee that the employee has developed signs or
						  symptoms commonly associated with lead intoxication, that the employee desires
						  medical advice regarding lead exposure and the ability to procreate a healthy
						  child, or that the employee has demonstrated difficulty in breathing during a
						  respirator fitting test or during respirator use. An examination is also to be
						  made available to each employee removed from exposure to lead due to a risk of
						  sustaining material impairment to health, or otherwise limited or specially
						  protected pursuant to medical recommendations.
Results of biological monitoring or the recommendations
						  of an examining physician may necessitate removal of an employee from further
						  lead exposure pursuant to the standard's medical removal protection (MRP)
						  program. The objective of the MRP program is to provide temporary medical
						  removal to workers either with substantially elevated blood lead levels or
						  otherwise at risk of sustaining material health impairment from continued
						  substantial exposure to lead. The guidelines which are summarized in the
						  following table were created under the standard for the temporary removal of an
						  exposed employee and his or her subsequent return to work in an exposure
						  area.
A.
Blood lead level requiring employee
								  medical removal. (Level must be confirmed with second follow-up blood lead
								  level within two weeks of first report.)
>60 [MICRO]g/100 g or
								  average of last three blood samples over previous 6 months (whichever is over a
								  longer time period) is 50 [MICRO]g/100g or greater unless last blood sample is
								  40 [MICRO]g/100g or less.
B.
Frequency which employees exposed to
								  action level of lead (30 [MICRO]g/m/TWA) must have blood level checked (ZPP is
								  also strongly recommended in each occasion that a blood lead is
								  obtained):
1. Last blood lead level less than 40
								  [MICRO]g/100g
Every 6 months.
2. Last blood lead level between 40
								  [MICRO]g/100g and level requiring medical removal (see A above)
Every 2
								  months.
3. Employees removed from exposure to
								  lead because of an elevated blood lead level.
Every 1 month.
C.
Permissible airborne exposure limit
								  for workers removed from work due to an elevated blood lead level (without
								  regard to respirator protection).
<30
								  [MICRO]g/m3 8 hr. TWA.
D.
Blood lead level confirmed with a
								  second blood analysis at which employee may return to work.
[LESS THAN
								  EQUAL TO] 40 [MICRO]g/100 g.
Note:
When medical opinion indicates that
						  an employee is at risk of material impairment from exposure to lead, the
						  physician can remove an employee from exposures exceeding the action level (or
						  less) or recommend special protective measures as deemed appropriate and
						  necessary. Medical monitoring during the medical removal period can be more
						  stringent than noted in the table above if the physician so specifies. Return
						  to work or removal of limitations and special protection is permitted when the
						  physician indicates that the worker is no longer at risk of material
						  impairment.
Under the standard's ultimate worker removal criteria,
						  a worker is to be removed from any work having any eight-hour TWA exposure to
						  lead of 30 [MICRO]g/M3 or more (without regard to
						  the use of respirators) whenever either of the following circumstances apply:
						  (1) a blood lead level of 60 [MICRO]g/100g or greater is obtained and confirmed
						  by a second follow-up blood lead level performed within two weeks after the
						  employer receives the results of the first blood sampling test, or (2) the
						  average of the previous three blood lead determinations or the average of all
						  blood lead determinations conducted during the previous six months, whichever
						  encompasses the longest time period, equals or exceeds 50 [MICRO]g/100g, unless
						  the last blood sample indicates a blood lead level at or below 40 [MICRO]g/100g
						  in which case the employee need not be removed. Medical removal is to continue
						  until two consecutive blood lead levels are 40 [MICRO]g/100g or less.
As part of the standard, the employer is required to
						  notify in writing each employee whose blood lead level exceeds 40
						  [MICRO]g/100g. In addition each such employee is to be informed that the
						  standard requires medical removal with MRP benefits, discussed below, when an
						  employee's blood lead level exceeds the above defined limits.
In addition to the above blood lead level criteria,
						  temporary worker removal may also take place as a result of medical
						  determinations and recommendations. A written medical opinion must be prepared
						  after each examination pursuant to the standard. If the examining physician
						  includes a medical finding, determination or opinion that the employee has a
						  medical condition which places the employee at increased risk of material
						  health impairment from exposure to lead, then the employee must be removed from
						  exposure to lead at or above the action level. Alternatively, if the examining
						  physician recommends special protective measures for an employee (e.g., use of
						  a powered air purifying respirator) or recommends limitations on an employee's
						  exposure to lead, then the employer must implement these recommendations.
						  Recommendations may be more stringent than the specific provisions of the
						  standard. The examining physician, therefore, is given broad flexibility to
						  tailor special protective procedures to the needs of individual employees. This
						  flexibility extends to the evaluation and management of pregnant workers and
						  male and female workers who are planning to raise children. Based on the
						  history, physical examination, and laboratory studies, the physician might
						  recommend special protective measures or medical removal for an employee who is
						  pregnant or who is planning to conceive a child when, in the physician's
						  judgement, continued exposure to lead at the current job would pose a
						  significant risk. The return of the employee to his or her former job status,
						  or the removal of special protections or limitations, depends upon the
						  examining physician determining that the employee is no longer at increased
						  risk of material impairment or that special measures are no longer
						  needed.
During the period of any form of special protection or
						  removal, the employer must maintain the worker's earnings, seniority, and other
						  employment rights and benefits (as though the worker had not been removed) for
						  a period of up to 18 months. This economic protection will maximize meaningful
						  worker participation in the medical surveillance program, and is appropriate as
						  part of the employer's overall obligation to provide a safe and healthful
						  workplace. The provisions of MRP benefits during the employee's removal period
						  may, however, be conditioned upon participation in medical surveillance.
On rare occasions, an employee's blood lead level may
						  not acceptably decline within 18 months of removal. This situation will arise
						  only in unusual circumstances, thus the standard relies on an individual
						  medical examination to determine how to protect such an employee. This medical
						  determination is to be based on both laboratory values, including lead levels,
						  zinc protoporphyrin levels, blood counts, and other tests felt to be warranted,
						  as well as the physician's judgment that any symptoms or findings on physical
						  examination are a result of lead toxicity. The medical determination may be
						  that the employee is incapable of ever safely returning to his or her former
						  job status. The medical determination may provide additional removal time past
						  18 months for some employees or specify special protective measures to be
						  implemented.
The lead standard provides for a multiple physician
						  review in cases where the employee wishes a second opinion concerning potential
						  lead poisoning or toxicity. If an employee wishes a second opinion, he or she
						  can make an appointment with a physician of his or her choice. This second
						  physician will review the findings, recommendations or determinations of the
						  first physician and conduct any examinations, consultations or tests deemed
						  necessary in an attempt to make a final medical determination. If the first and
						  second physicians do not agree in their assessment they must try to resolve
						  their differences. If they cannot reach an agreement then they must designate a
						  third physician to resolve the dispute.
The employer must provide examining and consulting
						  physicians with the following specific information: a copy of the lead standard
						  and all appendices, a description of the employee's duties as related to
						  exposure, the exposure level to lead and any other toxic substances (if
						  applicable), a description of personal protective equipment used, blood lead
						  levels, and all prior written medical opinions regarding the employee in the
						  employer's possession or control. The employer must also obtain from the
						  physician and provide the employee with a written medical opinion containing
						  blood lead levels, the physician's opinion as to whether the employee is at
						  risk of material impairment to health, any recommended protective measures for
						  the employee if further exposure is permitted, as well as any recommended
						  limitations upon an employee's use of respirators.
Employers must instruct each physician not to reveal to
						  the employer in writing or in any other way his or her findings, laboratory
						  results, or diagnoses which are felt to be unrelated to occupational lead
						  exposure.
They must also instruct each physician to advise the
						  employee of any occupationally or non-occupationally related medical condition
						  requiring further treatment or evaluation.
The standard provides for the use of respirators where
						  engineering and other primary controls have not been fully implemented.
						  However, the use of respirator protection shall not be used in lieu of
						  temporary medical removal due to elevated blood lead levels or findings that an
						  employee is at risk of material health impairment. This is based on the
						  numerous inadequacies of respirators including skin rash where the facepiece
						  makes contact with the skin, unacceptable stress to breathing in some workers
						  with underlying cardiopulmonary impairment, difficulty in providing adequate
						  fit, the tendency for respirators to create additional hazards by interfering
						  with vision, hearing, and mobility, and the difficulties of assuring the
						  maximum effectiveness of a complicated work practice program involving
						  respirators. Respirators do, however, serve a useful function where engineering
						  and work practice controls are inadequate by providing supplementary, interim,
						  or short-term protection, provided they are properly selected for the
						  environment in which the employee will be working, properly fitted to the
						  employee, maintained and cleaned periodically, and worn by the employee when
						  required.
Prophylactic chelation is prohibited by the lead
						  standard. Diagnostic and therapeutic chelation are permitted only under the
						  supervision of a licensed physician with appropriate medical monitoring in an
						  acceptable clinical setting. The decision to initiate chelation therapy must be
						  made on an individual basis and must take into account the severity of symptoms
						  felt to be a result of lead toxicity along with blood lead levels, ZPP levels,
						  and other laboratory tests as appropriate. EDTA and penicillamine, which are
						  the primary chelating agents used in the therapy of occupational lead
						  poisoning, have significant potential side effects and their use must be
						  justified on the basis of expected benefits to the worker. Unless frank and
						  severe symptoms are present, therapeutic chelation is not recommended, given
						  the opportunity to remove a worker from exposure and allow the body to
						  naturally excrete accumulated lead. As a diagnostic aid, the chelation
						  mobilization test using Ca-EDTA has limited applicability. According to some
						  investigators, the test can differentiate between lead-induced and other
						  nephropathies. The test may also provide an estimation of the mobile fraction
						  of the total body lead burden.
Employers are required to assure that accurate records
						  are maintained on exposure monitoring, medical surveillance, and medical
						  removal for each employee. Exposure monitoring and medical surveillance records
						  must be kept for 40 years or the duration of employment plus 20 years,
						  whichever is longer, while medical removal records must be maintained for the
						  duration of employment. All records required under the standard must be
						  available upon request to the Chief of the Division of Occupational Safety and
						  Health and the Director of the National Institute for Occupational Safety and
						  Health. Employees must also make environmental and biological monitoring and
						  medical removal records available to affected employees and to former employees
						  or their authorized employee representatives. Employees or their specifically
						  designated representatives have access to their entire medical surveillance
						  records.
In addition, the standard requires that the employer
						  inform all workers exposed to lead at or above the action level of the
						  provisions of the standard and all its appendices, the purpose and description
						  of medical surveillance and provisions for medical removal protection if
						  temporary removal is required. An understanding of the potential health effects
						  of lead exposure by all exposed employees along with full understanding of
						  their rights under the lead standard is essential for an effective monitoring
						  program.
II. Adverse health effects of inorganic lead
Although the toxicity of lead has been known for 2,000
						  years, the knowledge of the complex relationship between lead exposure and
						  human response is still being refined. Significant research into the toxic
						  properties of lead continues throughout the world, and it should be anticipated
						  that our understanding of thresholds of effects and margin of safety will be
						  improved in future years. The provisions of the lead standard are founded on
						  two prime medical judgments: first, the prevention of adverse health effects
						  from exposure to lead throughout a working lifetime requires that worker blood
						  lead levels be maintained at or below 40 [MICRO]g/100g; and second, the blood
						  lead levels of workers, male or female, who intend to parent in the near future
						  should be maintained below 30 [MICRO]g/100g to minimize adverse reproductive
						  health effects to the parents and developing fetus. The adverse effects of lead
						  on reproduction are being actively researched and the physician is encouraged
						  to remain abreast of recent developments in the area to best advise pregnant
						  workers or workers planning to conceive children.
The spectrum of health effects caused by lead exposure
						  can be subdivided into five developmental stages: normal, physiological changes
						  of uncertain significance, overt symptoms (morbidity), and mortality. Within
						  this process there are no sharp distinctions, but rather a continuum of
						  effects. Boundaries between categories overlap due to the wide variation of
						  individual responses and exposures in the working population. The development
						  of the lead standard focused on pathophysiological changes as well as later
						  stages of disease.
1. Heme Synthesis Inhibition. The earliest demonstrated
						  effect of lead involves its ability to inhibit at least two enzymes of the heme
						  synthesis pathway at very low blood lead levels. Inhibition of delta
						  aminolevulinic acid dehydrase (ALA-D) which catalyzes the conversion of
						  delta-aminolevulinic acid (ALA) to protoporphyrin is observed at a blood lead
						  level below 20 [MICRO]g/100g of whole blood. At a blood lead level of 40
						  [MICRO]g/100g, more than 20% of the population would have 70% inhibition of
						  ALA-D. There is an exponential increase in ALA excretion at blood lead levels
						  greater than 40 [MICRO]g/100g.
Another enzyme, ferrochelatase, is also inhibited at
						  low blood lead levels. Inhibition of ferrochelatase leads to increase free
						  erythrocyte protoporphyrin (FEP) in the blood which can then bind to zinc to
						  yield zinc protoporphyrin (ZPP). At a blood lead level of 50 [MICRO]g/100g or
						  greater, nearly 100% of the population will have an increase in FEP. There is
						  also an exponential relationship between blood lead levels greater than 40
						  [MICRO]g/100g and the associated ZPP level, which has led to the development of
						  the ZPP screening test for lead exposure.
While the significance of these effects is subject to
						  debate, these enzymatic disturbances may be early stages of a disease process
						  which eventually results in the clinical symptoms of lead poisoning. Whether or
						  not the effects do progress to the later stages of clinical disease, disruption
						  of these enzymatic processes over a working lifetime is considered to be a
						  material impairment of health.
One of the eventual results of lead-induced inhibition
						  of enzymes in the heme synthesis pathway is anemia which can be asymptomatic if
						  mild but associated with a wide array of symptoms including dizziness, fatigue,
						  and tachycardia when more severe. Studies have indicated that lead levels as
						  low as 50 [MICRO]g/100g can be associated with a definite decreased hemoglobin,
						  although most cases of lead-induced anemia, as well as shortened red-cell
						  survival times, occur at lead levels exceeding 80 [MICRO]g/100g. Inhibited
						  hemoglobin synthesis is more common in chronic cases whereas shortened
						  erythrocyte life span is more common in acute cases.
In lead-induced anemias, there is usually a
						  reticulocytosis along with the presence of basophilic stippling, and ringed
						  sideroblasts, although none of the above are pathognomonic for lead-induced
						  anemia.
2. Neurological Effects. Inorganic lead has been found
						  to have toxic effects on both the central and peripheral nervous systems. The
						  earliest stages of lead-induced central nervous system effects are manifested
						  by behavioral disturbances and central nervous system symptoms including
						  irritability, restlessness, insomnia and other sleep disturbances, fatigue,
						  vertigo, headache, poor memory, tremor, depression, and apathy. With more
						  severe exposure, symptoms can progress to drowsiness, stupor, hallucinations,
						  delirium, convulsions and coma.
The most severe and acute form of lead poisoning which
						  usually follows ingestion or inhalation of large amounts of lead is acute
						  encephalopathy which may arise precipitously with the onset of intractable
						  seizures, coma, cardiorespiratory arrest, and death within 48 hours.
While there is disagreement about what exposure levels
						  are needed to produce the earliest symptoms, most experts agree that symptoms
						  definitely can occur at blood lead levels of 60 [MICRO]g/100g whole blood and
						  therefore recommend a 40 [MICRO]g/100g maximum. The central nervous system
						  effects frequently are not reversible following discontinued exposure or
						  chelation therapy and when improvement does occur, it is almost always only
						  partial.
The peripheral neuropathy resulting from lead exposure
						  characteristically involves only motor function with minimal sensory damage and
						  has a marked predilection for the extensor muscles of the most active
						  extremity. The peripheral neuropathy can occur with varying degrees of
						  severity. The earliest and mildest form which can be detected in workers with
						  blood lead levels as low as 50 [MICRO]g/100g is manifested by slowing of motor
						  nerve conduction velocity often without clinical symptoms. With progression of
						  the neuropathy there is development of painless extensor muscle weakness
						  usually involving the extensor muscles of the fingers and hand in the most
						  active upper extremity, followed in severe cases by wrist drop or, much less
						  commonly, foot drop.
In addition to slowing of nerve conduction,
						  electromyographical studies in patients with blood lead levels greater than 50
						  [MICRO]g/100g have demonstrated a decrease in the number of acting motor unit
						  potentials, an increase in the duration of motor unit potentials, and
						  spontaneous pathological activity including fibrillations and fasciculations.
						  Whether these effects occur at levels of 40 [MICRO]g/100g is
						  undetermined.
While the peripheral neuropathies can occasionally be
						  reversed with therapy, again such recovery is not assured particularly in the
						  more severe neuropathies and often improvement is only partial. The lack of
						  reversibility is felt to be due in part to segmental demyelination.
3. Gastrointestinal. Lead may also affect the
						  gastrointestinal system producing abdominal colic or diffuse abdominal pain,
						  constipation, obstipation, diarrhea, anorexia, nausea and vomiting. Lead colic
						  rarely develops at blood lead levels below 80 [MICRO]g/100g.
4. Renal. Renal toxicity represents one of the most
						  serious health effects of lead poisoning. In the early stages of disease
						  nuclear inclusion bodies can frequently be identified in proximal renal tubular
						  cells. Renal function remains normal and the changes in this stage are probably
						  reversible. With more advanced disease there is progressive interstitial
						  fibrosis and impaired renal function. Eventually extensive interstitial
						  fibrosis ensues with sclerotic glomeruli and dilated and atrophied proximal
						  tubules; all represent end stage kidney disease. Azotemia can be progressive,
						  eventually resulting in frank uremia necessitating dialysis. There is
						  occasionally associated hypertension and hyperuricemia with or without
						  gout.
Early kidney disease is difficult to detect. The
						  urinalysis is normal in early lead nephropathy and the blood urea nitrogen and
						  serum creatinine increase only when two-thirds of kidney function is lost.
						  Measurement of creatinine clearance can often detect earlier disease as can
						  other methods of measurement of glomerular filtration rate. An abnormal Ca-EDTA
						  mobilization test has been used to differentiate between lead-induced and other
						  nephropathies, but this procedure is not widely accepted. A form of Fanconi
						  syndrome with aminoaciduria, glycosuria, and hyperphosphaturia indicating
						  severe injury to the proximal renal tubules is occasionally seen in
						  children.
5. Reproductive effects. Exposure to lead can have
						  serious effects on reproductive function in both males and females. In male
						  workers exposed to lead there can be a decrease in sexual drive, impotence,
						  decreased ability to produce healthy sperm, and sterility. Malformed sperm
						  (teratospermia), decreased number of sperm (hypospermia), and sperm with
						  decreased motility (asthenospermia) can all occur. Teratospermia has been noted
						  at mean blood lead levels of 53 [MICRO]g/100g and hypospermia and
						  asthenospermia at 41 [MICRO]g/100g. Furthermore, there appears to be
						  adose-response relationship for teratospermia in lead exposed workers.
Women exposed to lead may experience menstrual
						  disturbances including dysmenorrhea, menorrhagia and amenorrhea. Following
						  exposure to lead, women have a higher frequency of sterility, premature births,
						  spontaneous miscarriages, and stillbirths.
Germ cells can be affected by lead and cause genetic
						  damage in the egg or sperm cells before conception and result in failure to
						  implant, miscarriage, stillbirth, or birth defects.
Infants of mothers with lead poisoning have a higher
						  mortality during the first year and suffer from lowered birth weights, slower
						  growth, and nervous system disorders.
Lead can pass through the placental barrier and lead
						  levels in the mother's blood are comparable to concentrations of lead in the
						  umbilical cord at birth. Transplacental passage becomes detectable at 12-14
						  weeks of gestation and increases until birth.
There is little direct data on damage to the fetus from
						  exposure to lead but it is generally assumed that the fetus and newborn would
						  be at least as susceptible to neurological damage as young children. Blood lead
						  levels of 50-60 [MICRO]g/100g in children can cause significant neurobehavioral
						  impairments and there is evidence of hyperactivity at blood lead levels as low
						  as 25 [MICRO]g/100g. Given the overall body of literature concerning the
						  adverse health effects of lead in children, it is recommended that the blood
						  lead level in children should be maintained below 30 [MICRO]g/100g with a
						  population mean of 15 [MICRO]g/100g. Blood lead levels in the fetus and newborn
						  likewise should not exceed 30 [MICRO]g/100g.
Because of lead's ability to pass through the placental
						  barrier and also because of the demonstrated adverse effects of lead on
						  reproductive function in both the male and female as well as the risk of
						  genetic damage of lead on both the ovum and sperm, a 30 [MICRO]g/100g maximum
						  permissible blood lead level is recommended for both males and females who wish
						  to bear children.
6. Other toxic effects. Debate and research continue on
						  the effects of lead on the human body. Hypertension has frequently been noted
						  in occupationally exposed individuals although it is difficult to assess
						  whether this is due to lead's adverse effects on the kidney or if some other
						  mechanism is involved. Vascular and electrocardiographic changes have been
						  detected but have not been well characterized. Lead is thought to impair
						  thyroid function and interfere with the pituitary-adrenal axis, but again these
						  effects have not been well defined.
III. Medical Evaluation
The most important principle in evaluating a worker for
						  any occupational disease including lead poisoning is a high index of suspicion
						  on the part of the examining physician. As discussed in Section II, lead can
						  affect numerous organ systems and produce a wide array of signs and symptoms,
						  most of which are non-specific and subtle in nature at least in the early
						  stages of disease. Unless serious concern for lead toxicity is present, many of
						  the early clues to diagnosis may easily be overlooked.
The crucial initial step in the medical evaluation is
						  recognizing that a worker's employment can result in exposure to lead. The
						  worker will frequently be able to define exposures to lead and lead-containing
						  materials but often will not volunteer this information unless specifically
						  asked. In other situations the worker may not know of any exposures to lead but
						  the suspicion might be raised on the part of the physician because of the
						  industry or occupation of the worker. Potential occupational exposure to lead
						  and its compounds occur in at least 120 occupations, including lead smelting,
						  the manufacture of lead storage batteries, the manufacture of lead pigments and
						  products containing pigments, solder manufacture, shipbuilding and ship repair,
						  auto manufacturing, construction, and painting.
Once the possibility for lead exposure is known, the
						  focus can then be directed toward eliciting information from the medical
						  history, physical examination, and finally from laboratory data to evaluate the
						  worker for potential lead toxicity.
A complete and detailed work history is important in
						  the initial evaluation. A listing of all previous employment with information
						  on work processes, exposure to fumes or dust, known exposures to lead or other
						  toxic substances, respiratory protection used, and previous medical
						  surveillance should all be included in the worker's record. Where exposure to
						  lead is suspected, information concerning on-the-job personal hygiene, smoking
						  or eating habits in work areas, laundry procedures, and use of any protective
						  clothing or respiratory protection equipment should be noted. A complete work
						  history is essential in the medical evaluation of a worker with suspected lead
						  toxicity, especially when long term effects such as neurotoxicity and
						  nephrotoxicity are considered.
The medical history is also of fundamental importance
						  and should include a listing of all past and current medical conditions,
						  current medications including proprietary drug intake, previous surgeries and
						  hospitalizations, allergies, smoking history, alcohol consumption, and also
						  non-occupational lead exposures such as hobbies (hunting, riflery). Also known
						  childhood exposures should be elicited. Any previous history of hematological,
						  neurological, gastrointestinal, renal, psychological, gynecological, genetic,
						  or reproductive problems should be specifically noted.
A careful and complete review of systems must be
						  performed to assess both recognized complaints and subtle or slowly acquired
						  symptoms which the worker might not appreciate as being significant. The review
						  of symptoms should include the following:
General weight loss, fatigue, decreased
						  appetite.
Head, Eyes, Ears, Nose, Throat (HEENT) headaches,
						  visual disturbances or decreased visual acuity, hearing deficits or tinnitus,
						  pigmentation of the oral mucosa, or metallic taste in mouth.
Cardiopulmonary shortness of breath, cough, chest
						  pains, palpitations, or orthopnea.
Gastrointestinal nausea, vomiting, heartburn, abdominal
						  pain, constipation or diarrhea.
Neurologic irritability, insomnia, weakness (fatigue),
						  dizziness, loss of memory, confusion, hallucinations, incoordination, ataxia,
						  decreased strength in hands or feet, disturbances in gait, difficulty in
						  climbing stairs, or seizures.
Hematologic pallor, easily fatigued, abnormal blood
						  loss, melena.
Reproductive (male and female and spouse where
						  relevant) history of infertility, impotence, loss of libido, abnormal menstrual
						  periods, history of miscarriages, stillbirths, or children with birth
						  defects.
Musculo-skeletal muscle and joint pains.
The physical examination should emphasize the
						  neurological, gastrointestinal, and cardiovascular systems. The worker's weight
						  and blood pressure should be recorded and the oral mucosa checked for
						  pigmentation characteristic of a possible Burtonian or lead line on the
						  gingiva. It should be noted, however, that the lead line may not be present
						  even in severe lead poisoning if good oral hygiene is practiced.
The presence of pallor on skin examination may indicate
						  an anemia, which if severe might also be associated with a tachycardia. If an
						  anemia is suspected, an active search for blood loss should be undertaken
						  including potential blood loss through the gastrointestinal tract.
A complete neurological examination should include an
						  adequate mental status evaluation including a search for behavioral and
						  psychological disturbances, memory testing, evaluation for irritability,
						  insomnia, hallucinations, and mental clouding. Gait and coordination should be
						  examined along with close observation for tremor. A detailed evaluation of
						  peripheral nerve function including careful sensory and motor function testing
						  is warranted. Strength testing particularly of extensor muscle groups of all
						  extremities is of fundamental importance.
Cranial nerve evaluation should also be included in the
						  routine examination.
The abdominal examination should include auscultation
						  for bowel sounds and abdominal bruits and palpation for organomegaly, masses,
						  and diffuse abdominal tenderness.
Cardiovascular examination should evaluate possible
						  early signs of congestive heart failure. Pulmonary status should be addressed
						  particularly if respirator protection is contemplated.
As part of the medical evaluation, the lead standard
						  requires the following laboratory studies:
1. Blood lead level.
2. Hemoglobin and hematocrit determinations, red cell
						  indices, and examination of the peripheral blood smear to evaluate red blood
						  cell morphology.
3. Blood urea nitrogen.
4. Serum creatinine.
5. Routine urinalysis with microscopic
						  examination.
6. A zinc protoporphyrin level.
In addition to the above, the physician is authorized
						  to order any further laboratory or other tests which he or she deems necessary
						  in accordance with sound medical practice. The evaluation must also include
						  pregnancy testing or laboratory evaluation of male fertility if requested by
						  the employee.
Additional tests which are probably not warranted on a
						  routine basis but may be appropriate when blood lead and ZPP levels are
						  equivocal include delta-aminolevulinic acid and coproporphyrin concentrations
						  in the urine, and dark-field illumination for detection of basophilic stippling
						  in red blood cells.
If an anemia is detected further studies including a
						  careful examination of the peripheral smear, reticulocyte count, stool for
						  occult blood, serum iron, total iron binding capacity, bilirubin, and, if
						  appropriate, vitamin B12 and folate may be of value in attempting to identify
						  the cause of the anemia.
If a peripheral neuropathy is suspected, nerve
						  conduction studies are warranted both for diagnosis and as a basis to monitor
						  any therapy.
If renal disease is questioned, a 24-hour urine
						  collection for creatinine clearance, protein, and electrolytes may be
						  indicated. Elevated uric acid levels may result from lead-induced renal disease
						  and a serum uric acid level might be performed.
An electrocardiogram and chest X-ray may be obtained as
						  deemed appropriate.
Sophisticated and highly specialized testing should not
						  be done routinely and where indicated should be under the direction of a
						  specialist.
IV. Laboratory Evaluation
The blood lead level at present remains the single most
						  important test to monitor lead exposure and is the test used in the medical
						  surveillance program under the lead standard to guide employee medical removal.
						  The ZPP has several advantages over the blood lead level, but because of its
						  relatively recent development and the lack of extensive data concerning its
						  interpretation, the ZPP currently remains an ancillary test.
This section will discuss the blood lead level and ZPP
						  in detail and will outline their relative advantages and disadvantages. Other
						  blood tests currently available to evaluate lead exposure will also be
						  reviewed.
The blood lead level is a good index of current or
						  recent lead absorption when there is no anemia present and when the worker has
						  not taken any chelating agents. However, blood lead levels along with urinary
						  lead levels do not necessarily indicate the total body burden of lead and are
						  not adequate measures of past exposure. One reason for this is that lead has a
						  high affinity for bone and up to 90% of the body's total lead is deposited
						  there. A very important component of the total lead body burden is lead in soft
						  tissue (liver, kidney, and brain). This fraction of the lead body burden, the
						  biologically active lead, is not entirely reflected by blood lead levels since
						  it is a function of the dynamics of lead absorption, distribution, deposition
						  in bone and excretion. Following discontinuation of exposure to lead, the
						  excess body burden is only slowly mobilized from bone and other relatively
						  stable body stores and excreted. Consequently, a high blood lead level may only
						  represent recent heavy exposure to lead without a significant total body excess
						  and likewise a low blood lead level does not exclude an elevated total body
						  burden of lead.
Also, due to its correlation with recent exposures, the
						  blood lead level may vary considerably over short time intervals.
To minimize laboratory error and erroneous results due
						  to contamination, blood specimens must be carefully collected (after thorough
						  cleaning of the skin with appropriate methods) using lead-free blood containers
						  and analyzed by a reliable laboratory. Under the standard, samples must be
						  analyzed in laboratories which are approved by the Center of Disease Control
						  (CDC) or which have received satisfactory grades in proficiency testing by the
						  CDC in the previous year. Analysis is to be made using atomic absorption
						  spectrophotometry, anodic stripping voltammetry or any method which meets the
						  accuracy requirements set forth by the standard.
The determination of lead in urine is generally
						  considered a less reliable monitoring technique than analysis of whole blood
						  primarily due to individual variability in urinary excretion capacity as well
						  as the technical difficulty of obtaining accurate 24-hour urine collections. In
						  addition, workers with renal insufficiency,whether due to lead or some other
						  cause, may have decreased lead clearances and consequently urine lead levels
						  may underestimate the true lead burden. Therefore, urine lead levels should not
						  be used as a routine test.
The zinc protoporphyrin test, unlike the blood lead
						  determination, measures an adverse metabolic effect of lead and as such is a
						  better indicator of lead toxicity than the level of blood lead itself. The
						  level of ZPP reflects lead absorption over the preceding 3 to 4 months, and
						  therefore is a better indicator of lead body burden. The ZPP requires more time
						  than the blood lead to reach significantly elevated levels; the return to
						  normal after discontinuing lead exposure is also slower. Furthermore, the ZPP
						  test is simpler, faster, and less expensive to perform and no contamination is
						  possible. Many investigators believe it is the most reliable means of
						  monitoring chronic lead absorption.
Zinc protoporphyrin results from the inhibition of the
						  enzyme ferrochelatase which catalyzes the insertion of an iron molecule into
						  the protoporphyrin molecule, which then becomes heme. If iron is not inserted
						  into the molecule then zinc, having a greater affinity for protoporphrin, takes
						  the place of the iron, forming ZPP.
An evaluation in the level of circulating ZPP may occur
						  at blood lead levels as low as 20-30 [MICRO]g/100g in some workers. Once the
						  blood lead level has reached 40 [MICRO]g/100g there is more marked rise in the
						  ZPP value from its normal range of less than 100 g/100ml. Increases in blood
						  lead levels beyond 40 [MICRO]g/100g are associated with exponential increases
						  in ZPP.
Whereas blood lead levels fluctuate over short time
						  spans, ZPP levels remain relatively stable. ZPP is measured directly in red
						  blood cells and is present for the cell's entire 120-day life span. Therefore,
						  the ZPP level in blood reflects the average ZPP production over the previous
						  3-4 months and consequently the average lead exposure during that time
						  interval.
It is recommended that a hematocrit be determined
						  whenever a confirmed ZPP of 50 [MICRO]g/100ml whole blood is obtained to rule
						  out a significant underlying anemia. If the ZPP is in excess of 100 g/100ml and
						  not associated with abnormal elevations in blood lead levels, the laboratory
						  should be checked to be sure that blood leads were determined using atomic
						  absorption spectrophotometry, anodic stripping voltammetry or other method
						  meeting the accuracy requirements set forth by the standard and by a
						  CDC-approved laboratory which is experienced in lead level determinations.
						  Repeat periodic blood lead studies should be obtained in all individuals with
						  elevated ZPP levels to be certain that an associated elevated blood lead level
						  has not been missed due to transient fluctuations in blood leads.
ZPP has a characteristic fluorescence spectrum with a
						  peak at 594 nm which is detectable with a hematofluorimeter. The
						  hematofluorimeter is accurate and portable and can provide on-site,
						  instantaneous results for workers who can be frequently tested via a finger
						  prick.
However, careful attention must be given to calibration
						  and quality control procedures. Limited data on blood leadZPP correlations and
						  the ZPP levels which are associated with the adverse health effects discussed
						  in Section II are the major limitations of the test. Also it is difficult to
						  correlate ZPP levels with environmental exposure and there is some variation of
						  response with age and sex. Nevertheless, the ZPP promises to be an important
						  diagnostic test for the early detection of lead toxicity and its value will
						  increase as more data are collected regarding its relationship to other
						  manifestations of lead poisoning.
Levels of delta-aminolevulinic acid (ALA) in the urine
						  are also used as a measure of lead exposure. Increasing concentrations of ALA
						  are believed to result from the inhibition of the enzyme delta-aminolevulinic
						  acid dehydrase (ALA-D). Although the test is relatively easy to perform,
						  inexpensive, and rapid, the disadvantages include variability in results, the
						  necessity to collect a complete 24-hour urine sample which has a specific
						  gravity greater than 1.010, and also the fact that ALA decomposes in the
						  presence of light.
The pattern of porphyrin excretion in the urine can
						  also be helpful in identifying lead intoxication. With lead poisoning, the
						  urine concentrations of coproporphyrins I and II, porphobilinogen and
						  uroporphyrin I rise. The most important increase, however, is that of
						  coproporphyrin III; levels may exceed 5,000 [MICRO]g/1 in the urine in lead
						  poisoned individuals, but its correlation with blood lead levels and ZPP are
						  not as good as those of ALA. Increases in urinary prophyrins are not diagnostic
						  of lead toxicity and may be seen in porphyria, some liver diseases, and in
						  patients with high reticulocyte counts.
Summary. The standard for inorganic lead places
						  significant emphasis on the medical surveillance of all workers exposed to
						  levels of inorganic lead above the action level of 30
						  [MICRO]g/M3 TWA. The physician has a fundamental
						  role in this surveillance program, and in the operation of the medical removal
						  protection program.
Even with adequate worker education on the adverse
						  health effects of lead and appropriate training in work practices, personal
						  hygiene and other control measures, the physician has a primary responsibility
						  for evaluating potential lead toxicity in the worker. It is only through a
						  careful and detailed medical and work history, a complete physical examination
						  and appropriate laboratory testing that an accurate assessment can be made.
						  Many of the adverse health effects of lead toxicity are either irreversible or
						  only partially reversible and therefore early detection of disease is very
						  important.
This document outlines the medical monitoring program
						  as defined by the occupational safety and health standard for inorganic lead.
						  It reviews the adverse health effects of lead poisoning and describes the
						  important elements of the history and physical examinations as they relate to
						  these adverse effects.