Physician information.
(a) Introduction. The medical surveillance
provisions of WAC
296-62-07423
generally are aimed at accomplishing three main interrelated purposes: First,
identifying employees at higher risk of adverse health effects from excess,
chronic exposure to cadmium; second, preventing cadmium-induced disease; and
third, detecting and minimizing existing cadmium-induced disease. The core of
medical surveillance in this standard is the early and periodic monitoring of
the employee's biological indicators of:
(i)
Recent exposure to cadmium;
(ii)
Cadmium body burden; and
(iii)
Potential and actual kidney damage associated with exposure to cadmium. The
main adverse health effects associated with cadmium overexposure are lung
cancer and kidney dysfunction. It is not yet known how to adequately
biologically monitor human beings to specifically prevent cadmium-induced lung
cancer. By contrast, the kidney can be monitored to provide prevention and
early detection of cadmium-induced kidney damage. Since, for noncarcinogenic
effects, the kidney is considered the primary target organ of chronic exposure
to cadmium, the medical surveillance provisions of this standard effectively
focus on cadmium-induced kidney disease. Within that focus, the aim, where
possible, is to prevent the onset of such disease and, where necessary, to
minimize such disease as may already exist. The by-products of successful
prevention of kidney disease are anticipated to be the reduction and prevention
of other cadmium-induced diseases.
(b) Health effects. The major health effects
associated with cadmium overexposure are described below.
(i) Kidney: The most prevalent nonmalignant
disease observed among workers chronically exposed to cadmium is kidney
dysfunction. Initially, such dysfunction is manifested as proteinuria. The
proteinuria associated with cadmium exposure is most commonly characterized by
excretion of low-molecular weight proteins (15,000 to 40,000 MW) accompanied by
loss of electrolytes, uric acid, calcium, amino acids, and phosphate. The
compounds commonly excreted include: Beta-2-microglobulin
([BETA]2-M), retinol binding protein (RBP),
immunoglobulin light chains, and lyso-zyme. Excretion of low molecular weight
proteins are characteristic of damage to the proximal tubules of the kidney
(Iwao et al., 1980). It has also been observed that exposure to cadmium may
lead to urinary excretion of high-molecular weight proteins such as albumin,
immunoglobulin G, and glycoproteins (Ex. 29). Excretion of high-molecular
weight proteins is typically indicative of damage to the glomeruli of the
kidney. Bernard et al., (1979) suggest that damage to the glomeruli and damage
to the proximal tubules of the kidney may both be linked to cadmium exposure
but they may occur independently of each other. Several studies indicate that
the onset of low-molecular weight proteinuria is a sign of irreversible kidney
damage (Friberg et al., 1974; Roels et al., 1982; Piscator 1984; Elinder et
al., 1985; Smith et al., 1986). Above specific levels of
[BETA]2-M associated with cadmium exposure it is
unlikely that [BETA]2-M levels return to normal even
when cadmium exposure is eliminated by removal of the individual from the
cadmium work environment (Friberg, Ex. 29, 1990). Some studies indicate that
such proteinuria may be progressive; levels of [BETA]2-M
observed in the urine increase with time even after cadmium exposure has
ceased. See, for example, Elinder et al., 1985. Such observations, however, are
not universal, and it has been suggested that studies in which proteinuria has
not been observed to progress may not have tracked patients for a sufficiently
long time interval (Jarup, Ex. 8-661). When cadmium exposure continues after
the onset of proteinuria, chronic nephrotoxicity may occur (Friberg, Ex. 29).
Uremia results from the inability of the glomerulus to adequately filter blood.
This leads to severe disturbance of electrolyte concentrations and may lead to
various clinical complications including kidney stones (L-140-50). After
prolonged exposure to cadmium, glomerular proteinuria, glucosuria,
aminoaciduria, phosphaturia, and hypercalciuria may develop (Exs. 8-86, 4-28,
14-18). Phosphate, calcium, glucose, and amino acids are essential to life, and
under normal conditions, their excretion should be regulated by the kidney.
Once low molecular weight proteinuria has developed, these elements dissipate
from the human body. Loss of glomerular function may also occur, manifested by
decreased glomerular filtration rate and increased serum creatinine. Severe
cadmium-induced renal damage may eventually develop into chronic renal failure
and uremia (Ex. 55). Studies in which animals are chronically exposed to
cadmium confirm the renal effects observed in humans (Friberg et al., 1986).
Animal studies also confirm problems with calcium metabolism and related
skeletal effects which have been observed among humans exposed to cadmium in
addition to the renal effects. Other effects commonly reported in chronic
animal studies include anemia, changes in liver morphology, immunosuppression
and hypertension. Some of these effects may be associated with co-factors.
Hypertension, for example, appears to be associated with diet as well as
cadmium exposure. Animals injected with cadmium have also shown testicular
necrosis (Ex. 8-86B).
(ii)
Biological markers. It is universally recognized that the best measures of
cadmium exposures and its effects are measurements of cadmium in biological
fluids, especially urine and blood. Of the two, CdU is conventionally used to
determine body burden of cadmium in workers without kidney disease. CdB is
conventionally used to monitor for recent exposure to cadmium. In addition,
levels of CdU and CdB historically have been used to predict the percent of the
population likely to develop kidney disease (Thun et al., Ex. L-140-50; WHO,
Ex. 8-674; ACGIH, Exs. 8-667, 140-50). The third biological parameter upon
which WISHA relies for medical surveillance is beta-2-microglobulin in urine
([BETA]
2-M), a low molecular weight protein. Excess
[BETA]
2-M has been widely accepted by physicians and
scientists as a reliable indicator of functional damage to the proximal tubule
of the kidney (Exs. 8-447, 144-3-C, 4-47, L-140-45, 19-43-A). Excess
[BETA]
2-M is found when the proximal tubules can no
longer reabsorb this protein in a normal manner. This failure of the proximal
tubules is an early stage of a kind of kidney disease that commonly occurs
among workers with excessive cadmium exposure. Used in conjunction with
biological test results indicating abnormal levels of CdU and CdB, the finding
of excess [BETA]
2-M can establish for an examining
physician that any existing kidney disease is probably cadmium-related (Trs.
6/6/90, pp. 82-86, 122, 134). The upper limits of normal levels for cadmium in
urine and cadmium in blood are 3 µg Cd/gram creatinine in urine and 5
µgCd/liter whole blood, respectively. These levels were derived from
broad-based population studies. Three issues confront the physicians in the use
of [BETA]
2-M as a marker of kidney dysfunction and
material impairment. First, there are a few other causes of elevated levels of
[BETA]
2-M not related to cadmium exposures, some of
which may be rather common diseases and some of which are serious diseases
(e.g., myeloma or transient flu, Exs. 29 and 8-086). These can be medically
evaluated as alternative causes (Friberg, Ex. 29). Also, there are other
factors that can cause [BETA]
2-M to degrade so that low
levels would result in workers with tubular dysfunction. For example, regarding
the degradation of [BETA]
2-M, workers with acidic urine
(pH<6) might have [BETA]
2-M levels that are within
the "normal" range when in fact kidney dysfunction has occurred (Ex. L-140-1)
and the low molecular weight proteins are degraded in acid urine. Thus, it is
very important that the pH of urine be measured, that urine samples be buffered
as necessary (See WAC
296-62-07451,
appendix F.), and that urine samples be handled correctly, i.e., measure the pH
of freshly voided urine samples, then if necessary, buffer to Ph>6 (or above
for shipping purposes), measure Ph again and then, perhaps, freeze the sample
for storage and shipping. (See also WAC
296-62-07451,
appendix F.) Second, there is debate over the pathological significance of
proteinuria, however, most world experts believe that
[BETA]
2-M levels greater than 300 µg/g Cr are
abnormal (Elinder, Ex. 55, Friberg, Ex. 29). Such levels signify kidney
dysfunction that constitutes material impairment of health. Finally, detection
of [BETA]
2-M at low levels has often been considered
difficult, however, many laboratories have the capability of detecting excess
[BETA]
2-M using simple kits, such as the Phadebas
Delphia test, that are accurate to levels of 100 µg
[BETA]
2-M/g Cr U (Ex. L-140-1). Specific recommendations
for ways to measure [BETA]
2-M and proper handling of
urine samples to prevent degradation of [BETA]
2-M have
been addressed by WISHA in WAC
296-62-07451,
appendix F, in the section on laboratory standardization. All biological
samples must be analyzed in a laboratory that is proficient in the analysis of
that particular analyte, under WAC
296-62-07423(1)(d).
(See WAC
296-62-07451,
appendix F). Specifically, under WAC
296-62-07423(1)(d),
the employer is to ensure that the collecting and handling of biological
samples of cadmium in urine (CdU), cadmium in blood (CdB), and beta-2
microglobulin in urine ([BETA]
2-M) taken from employees
is collected in a manner that ensures reliability. The employer must also
ensure that analysis of biological samples of cadmium in urine (CdU), cadmium
in blood (CdB), and beta-2 microglobulin in urine
([BETA]
2-M) taken from employees is performed in
laboratories with demonstrated proficiency for that particular analyte. (See
WAC
296-62-07451,
appendix F).
(iii) Lung and
prostate cancer. The primary sites for cadmium-associated cancer appear to be
the lung and the prostate (L-140-50). Evidence for an association between
cancer and cadmium exposure derives from both epidemiological studies and
animal experiments. Mortality from prostate cancer associated with cadmium is
slightly elevated in several industrial cohorts, but the number of cases is
small and there is not clear dose-response relationship. More substantive
evidence exists for lung cancer. The major epidemiological study of lung cancer
was conducted by Thun et al., (Ex. 4-68). Adequate data on cadmium exposures
were available to allow evaluation of dose-response relationships between
cadmium exposure and lung cancer. A statistically significant excess of lung
cancer attributed to cadmium exposure was observed in this study even when
confounding variables such as co-exposure to arsenic and smoking habits were
taken into consideration (Ex. L-140-50). The primary evidence for quantifying a
link between lung cancer and cadmium exposure from animal studies derives from
two rat bioassay studies; one by Takenaka et al., (1983), which is a study of
cadmium chloride and a second study by Oldiges and Glaser (1990) of four
cadmium compounds. Based on the above cited studies, the U.S. Environmental
Protection Agency (EPA) classified cadmium as "B1," a probable human
carcinogen, in 1985 (Ex. 4-4). The International Agency for Research on Cancer
(IARC) in 1987 also recommended that cadmium be listed as "2A," a probable
human carcinogen (Ex. 4-15). The American Conference of Governmental Industrial
Hygienists (ACGIH) has recently recommended that cadmium be labeled as a
carcinogen. Since 1984, NIOSH has concluded that cadmium is possibly a human
carcinogen and has recommended that exposures be controlled to the lowest level
feasible.
(iv) Noncarcinogenic
effects. Acute pneumonitis occurs 10 to 24 hours after initial acute inhalation
of high levels of cadmium fumes with symptoms such as fever and chest pain
(Exs. 30, 8-86B). In extreme exposure cases pulmonary edema may develop and
cause death several days after exposure. Little actual exposure measurement
data is available on the level of airborne cadmium exposure that causes such
immediate adverse lung effects, nonetheless, it is reasonable to believe a
cadmium concentration of approximately 1 mg/m
3 over
an eight hour period is "immediately dangerous" (55 FR
4052, ANSI; Ex. 8-86B).
In addition to acute lung effects and chronic renal effects, long term exposure
to cadmium may cause other severe effects on the respiratory system. Reduced
pulmonary function and chronic lung disease indicative of emphysema have been
observed in workers who have had prolonged exposure to cadmium dust or fumes
(Exs. 4-29, 4-22, 4-42, 4-50, 4-63). In a study of workers conducted by
Kazantzis et al., a statistically significant excess of worker deaths due to
chronic bronchitis was found, which in his opinion was directly related to high
cadmium exposures of 1 mg/m
3 or more (Tr. 6/8/90,
pp. 156-157). Cadmium need not be respirable to constitute a hazard. Inspirable
cadmium particles that are too large to be respirable but small enough to enter
the tracheobronchial region of the lung can lead to bronchoconstriction,
chronic pulmonary disease, and cancer of that portion of the lung. All of these
diseases have been associated with occupational exposure to cadmium (Ex.
8-86B). Particles that are constrained by their size to the extra-thoracic
regions of the respiratory system such as the nose and maxillary sinuses can be
swallowed through mucocillary clearance and be absorbed into the body (ACGIH,
Ex. 8-692). The impaction of these particles in the upper airways can lead to
anosmia, or loss of sense of smell, which is an early indication of
overexposure among workers exposed to heavy metals. This condition is commonly
reported among cadmium-exposed workers (Ex. 8-86-B).
(c) Medical surveillance. In general, the
main provisions of the medical surveillance section of the standard, under WAC
296-62-07423(1) through
(16), are as follows:
(i) Workers exposed above the action level
are covered;
(ii) Workers with
intermittent exposures are not covered;
(iii)
Past workers who are covered receive biological monitoring for at
least one year;
(iv) Initial
examinations include a medical questionnaire and biological monitoring of
cadmium in blood (CdB), cadmium in urine (CdU), and Beta-2-microglobulin in
urine ([BETA]2-M);
(v)
Biological monitoring of these three analytes is performed at
least annually; full medical examinations are performed biennially;
(vi) Until five years from the effective
date of the standard, medical removal is required when CdU is greater than 15
µg/gram creatinine (g Cr), or CdB is greater than 15 µg/liter whole
blood (lwb), or [BETA]2-M is greater than 1500
µg/g Cr, and CdB is greater than 5 µg/lwb or CdU is greater than 3
µg/g Cr;
(vii) Beginning
five years after the standard is in effect, medical removal triggers will be
reduced;
(viii) Medical removal
protection benefits are to be provided for up to eighteen months;
(ix) Limited initial medical examinations
are required for respirator usage;
(x)
Major provisions are fully described under WAC
296-62-07423;
they are outlined here as follows:
(A)
Eligibility.
(B) Biological
monitoring.
(C) Actions triggered
by levels of CdU, CdB, and [BETA]
2-M (See Summary Charts
and Tables in WAC
296-62-07441(5).)
(D)
Periodic medical surveillance.
(E)
Actions triggered by periodic medical surveillance (See appendix
A Summary Chart and Tables in WAC
296-62-07441(5).)
(F) Respirator usage.
(G) Emergency medical
examinations.
(H) Termination
examination.
(I) Information to
physician.
(J) Physician's medical
opinion.
(K) Medical removal
protection.
(L) Medical removal
protection benefits.
(M) Multiple
physician review.
(N) Alternate
physician review.
(O) Information
employer gives to employee.
(P)
Recordkeeping.
(Q) Reporting on
OSHA form 200.
(xi) The
above mentioned summary of the medical surveillance provisions, the summary
chart, and tables for the actions triggered at different levels of CdU, CdB and
[BETA]
2-M (in subsection (5) of this section, Attachment
1) are included only for the purpose of facilitating understanding of the
provisions of WAC
296-62-07423(3)
of the final cadmium standard. The summary of the provisions, the summary
chart, and the tables do not add to or reduce the requirements in WAC
296-62-07423(3).
(d) Recommendations to
physicians.
(i) It is strongly recommended
that patients with tubular proteinuria are counseled on: The hazards of
smoking; avoidance of nephrotoxins and certain prescriptions and
over-the-counter medications that may exacerbate kidney symptoms; how to
control diabetes and/or blood pressure; proper hydration, diet, and exercise
(Ex. 19-2). A list of prominent or common nephrotoxins is attached. (See
subsection (6) of this section, Attachment 2.)
(ii) DO NOT CHELATE; KNOW WHICH DRUGS ARE
NEPHROTOXINS OR ARE ASSOCIATED WITH NEPHRITIS.
(iii) The gravity of cadmium-induced renal
damage is compounded by the fact there is no medical treatment to prevent or
reduce the accumulation of cadmium in the kidney (Ex. 8-619). Dr. Friberg, a
leading world expert on cadmium toxicity, indicated in 1992, that there is no
form of chelating agent that could be used without substantial risk. He stated
that tubular proteinuria has to be treated in the same way as other kidney
disorders (Ex. 29).
(iv) After the
results of a workers' biological monitoring or medical examination are received
the employer is required to provide an information sheet to the patient,
briefly explaining the significance of the results. (See subsection (7) of this
section.)
(v) For additional
information the physician is referred to the following additional resources:
(A) The physician can always obtain a copy
of the OSHA final rule preamble, with its full discussion of the health
effects, from OSHA's Computerized Information System (OCIS).
(B) The OSHA Docket Officer maintains a
record of the OSHA rulemaking. The Cadmium Docket (H-057A), is located at 200
Constitution Ave. NW., Room N-2625, Washington, DC 20210; telephone: (202)
219-7894.
(C) The following
articles and exhibits in particular from that docket (H-057A):
Exhibit number |
Author and paper title |
8-447 |
Lauwerys et. al., Guide for physicians, "Health
Maintenance of Workers Exposed to Cadmium," published by the Cadmium Council.
|
4-67 |
Takenaka, S., H. Oldiges, H. Konig, D. Hochrainer, G.
Oberdorster. "Carcinogenicity of Cadmium Chloride Aerosols in Wistar Rats."
JNCI 70:367-373, 1983. (32) |
4-68 |
Thun, M.J., T.M. Schnoor, A.B. Smith, W.E. Halperin,
R.A. Lemen. "Mortality Among a Cohort of U.S. Cadmium Production Workers-An
Update." JNCI 74(2):325-33, 1985. (8) |
4-25 |
Elinder, C.G., Kjellstrom, T., Hogstedt, C., et al.,
"Cancer Mortality of Cadmium Workers." Brit. J. Ind. Med. 42:651-655, 1985.
(14) |
4-26 |
Ellis, K.J. et al., "Critical Concentrations of Cadmium
in Human Renal Cortex: Dose Effect Studies to Cadmium Smelter Workers." J.
Toxicol. Environ. Health 7:691-703, 1981. (76) |
4-27 |
Ellis, K.J., S.H. Cohn and T.J. Smith. "Cadmium
Inhalation Exposure Estimates: Their Significance with Respect to Kidney and
Liver Cadmium Burden." J. Toxicol. Environ. Health 15:173-187, 1985. |
4-28 |
Falck, F.Y., Jr., Fine, L.J., Smith, R.G., McClatchey,
K.D., Annesley, T., England, B., and Schork, A.M. "Occupational Cadmium
Exposure and Renal Status." Am. J. Ind. Med. 4:541, 1983. (64) |
8-86A |
Friberg, L., C.G. Elinder, et al., "Cadmium and Health a
Toxicological and Epidemiological Appraisal, Volume I, Exposure, Dose, and
Metabolism." CRC Press, Inc., Boca Raton, FL, 1986. (Available from the OSHA
Technical Data Center) |
8-86B |
Friberg, L., C.G. Elinder, et al., "Cadmium and Health:
A Toxicological and Epidemiological Appraisal, Volume II, Effects and
Response." CRC Press, Inc., Boca Raton, FL, 1986. (Available from the OSHA
Technical Data Center) |
L-140-45 |
Elinder, C.G., "Cancer Mortality of Cadmium Workers,"
Brit. J. Ind. Med., 42, 651-655, 1985. |
L-140-50 |
Thun, M., Elinder, C.G., Friberg, L, "Scientific Basis
for an Occupational Standard for Cadmium, Am. J. Ind. Med., 20; 629-642, 1991.
|