Washington Administrative Code › Title 296 - Labor and Industries, Department of › Chapter 296-849 - Benzene › Section 296-849-60020 - Medical guidelines for benzene

Current through Register Vol. 24-14, July 15, 2024
(1) You must include an explanation
			 of the contents of this section to employees as required in Training,
			 WAC
			 296-849-11050.
(2) You must provide a copy of this
			 section to the licensed health care professional (LHCP) as required
			 in Step 4 of the medical evaluation process found in Medical
			 evaluations, WAC
			 296-849-12030.
Table 8
Medical Guidelines For Evaluating Employees
				Exposed to Benzene
Part 1: Becoming familiar
						with medical requirements in this chapter
In addition to requiring employers
						to train employees and protect them from exposure to benzene, this
						chapter (the Benzene rule) requires employers to monitor their
						employees' health with assistance from licensed health care
						professionals (LHCPs).
* For employees who will use
						respirators, the LHCP will also need to provide the employer with a
						written medical opinion clearing the employee for workplace
						respirator use.
These guidelines were designed to
						support an informed partnership between the LHCP and the employer
						when monitoring the health of employees exposed to benzene.
The employer initiates this
						partnership by providing the LHCP with a copy of the chapter and
						other supporting information about the employee and job conditions.
						The LHCP can then become familiar with the medical monitoring
						requirements found in WAC
						296-849-12030
						through
						296-849-12080,
						which address:
* Frequency and content for routine
						(initial and periodic) medical examinations and consultations;
* Emergency and other unplanned
						medical follow-up;
* Medical opinions;
* Employee medical removal;
* Medical records retention and
						content.
Part 2: Benzene
						toxicology
Benzene is primarily an inhalation
						hazard. Systematic absorption may cause depression of the
						hematopoietic system, pancytopenia, aplastic anemia, and leukemia.
						Clinical evidence of leukopenia, anemia, and thrombocytopenia, singly
						or in combination, has been frequently reported among the first
						signs.
Health information about
						benzene, WAC 296-848-50010,
provides
basic
						information
about the health effects and symptoms associated
						with benzene exposure.
Reference:
* Other sources for toxicology
						information include:
-
						ToxFAQsTM and the Toxicological Profile
						for Benzene. This free document is available from the Agency for
						Toxic Substances and Disease Registry (ATSDR) and can be obtained by:
* Visiting
http://www.atsdr.cdc.gov/toxprofiles
OR
* Calling 1-888-422-8737
- A variety of technical resources
						on benzene from the National Institutes for Occupational Safety and
						Health (NIOSH) by visiting http://www.cdc.niosh/topics/chemicals.html
						[File Link Not Available]
Part 3: Treatment of acute
						toxic effects
When providing assistance to
						someone contaminated with benzene, make sure
you
are
						adequately protected and do not risk being overcome by benzene vapor.
Remove the patient from exposure
						immediately.
Give oxygen or artificial
						resuscitation, if indicated.
Flush eyes, wash skin if
						contaminated and remove all contaminated clothing.
Recovery from mild exposures is
						usually rapid and complete. Symptoms of intoxication may persist
						following severe exposures.
Part 4: Preventive
						considerations
The principal effects of benzene
						exposure which form the basis for the requirements in this chapter
						are pathological changes in the hematopoietic system, reflected by
						changes in the peripheral blood and manifesting clinically as
						pancytopenia, aplastic anemia, and leukemia.
Consequently, the medical
						monitoring program is designed to observe, on a regular basis, blood
						indices for early signs of these effects, and although early signs of
						leukemia are not usually available, emerging diagnostic technology
						and innovative regimes make consistent surveillance for leukemia, as
						well as other hematopoietic effects, essential.
Symptoms and signs of benzene
						toxicity can be nonspecific. Only a detailed history and appropriate
						investigative procedure will enable a physician to rule out or
						confirm conditions that place the employee at increased risk.
Bone marrow may appear normal,
						aplastic, or hyperplastic, and may not, in all situations, correlate
						with peripheral blood forming tissues. Because of variations in the
						susceptibility to benzene morbidity, there is no "typical" blood
						picture. The onset of effects of prolonged benzene exposure may be
						delayed for many months or years after the actual exposure has ceased
						and identification or correlation with benzene exposure must be
						sought out in the occupational history.
There are special provisions for
						medical tests in the event of hematologic abnormalities or for
						emergency situations.
- This chapter specifies that blood
						abnormalities that persist must be referred "unless the physician has
						good reason to believe such referral is unnecessary." Examples of
						conditions that could make a referral unnecessary despite abnormal
						blood limits are iron or folate deficiency, menorrhagia, or blood
						loss due to some unrelated medical abnormality.
- Blood values that require
						referral to a hematologist or internist are noted under Part 5:
						Hematology guidelines.
Part 5: Hematology
						guidelines
The following guidelines are
						established to assist the examining LHCP with regard to which
						laboratory tests are necessary and when to refer an employee to the
						specialist. A minimum battery of tests is to be performed using
						strictly standardized methods.
Basic tests
* The following must be determined
						by an accredited laboratory:
- Red and white cell counts;
- Platelet counts;
- White blood cell differential;
- Hematocrit;
- Red cell indices.
* The normal ranges for the red
						cell and white cell counts are influenced by altitude, race, and sex,
						and therefore should be determined by the accredited laboratory in
						the specific area where the tests are performed.
* Either a decline from an absolute normal or
						  an individual's baseline to a subnormal value or a rise to a
						  supra-normal value, are indicative of potential toxicity,
						  particularly if all blood parameters decline.
- The normal total white blood
						count is approximately 7,200/mm3 plus or
						minus 3,000;
- For cigarette smokers the white
						count may be higher and the upper range may be 2,000 cells higher
						than normal for the laboratory;
- In addition, infection, allergies
						and some drugs may raise the white cell count;
- The normal platelet count is
						approximately 250,000 with a range of 140,000 to 400,000. Counts
						outside this range should be regarded as possible evidence of benzene
						toxicity.
* Certain abnormalities found
						through routine screening are of greater significance in the
						benzene-exposed worker and
require prompt consultation with a
						specialist,
namely:
- Thrombocytopenia;
- A trend of decreasing white cell,
						red cell, or platelet indices in an individual over time is more
						worrisome than an isolated abnormal finding at one test time. The
						importance of trend highlights the need to compare an individual's
						test results to baseline and/or previous periodic tests;
- A constellation or pattern of
						abnormalities in the different blood indices is of more significance
						than a single abnormality. A low white count not associated with any
						abnormalities in other cell indices may be a normal statistical
						variation, whereas if the low white count is accompanied by decreases
						in the platelet and/or red cell indices, such a pattern is more
						likely to be associated with benzene toxicity and merits thorough
						investigation;
* Anemia, leukopenia, macrocytosis or an
						  abnormal differential white blood cell count should alert the
						  physician to further investigate and/or refer the patient if repeat
						  tests confirm the abnormalities. If routine screening detects an
						  abnormality, follow-up tests which may be helpful in establishing the
						  etiology of the abnormality are the peripheral blood smear and the
						  reticulocyte count;
* The extreme range of normal for
						  reticulocytes is 0.4 to 2.5 percent of the red cells, the usual range
						  being 0.5 to 1.2 percent of the red cells, but the typical value is
						  in the range of 0.8 to 1.0 percent;
* A decline in reticulocytes to levels of
						  less than 0.4 percent is to be regarded as possible evidence (unless
						  another specific cause is found) of benzene toxicity requiring
						  accelerated surveillance. An increase in reticulocyte levels to about
						  2.5 percent may also be consistent with (but is not as characteristic
						  of) benzene toxicity.
Additional tests
1. Peripheral blood smears:
* Collecting the sample: As with
						reticulocyte count, the smear should be with fresh uncoagulated blood
						obtained from a needle tip following venipuncture or from a drop of
						earlobe blood (capillary blood). If necessary, the smear may, under
						certain limited conditions, be made from a blood sample
						anticoagulated with EDTA (but never with oxalate or heparin).
* Prepping the smear: When the
						smear is to be prepared from a specimen of venous blood which has
						been collected by a commercial Vacutainer type tube containing
						neutral EDTA, the smear should be made as soon as possible after the
						venesection. A delay of up to twelve hours is permissible between the
						drawing of the blood specimen into EDTA and the preparation of the
						smear if the blood is stored at refrigerator (not freezing)
						temperature.
* Minimum mandatory observations:
- The differential white blood cell
						count;
- Description of abnormaliries in
						the appearance of red cells;
- Description of any abnormalities
						in the platelets;
- A careful search must be made
						throughout of every blood smear for immature white cells such as band
						forms (in more than normal proportion, i.e., over 10 percent of the
						total differential count), any number of metamyelocytes, myelocytes,
						or myeloblasts. Any nucleate or multinucleated red blood cells should
						be reported. Large "giant" platelets or fragments of megakaryocytes
						must be recognized;
* An increase in the proportion of
						band forms among the neutrophilic granulocytes is an abnormality
						deserving special mention, for it may represent a change which should
						be considered as an early warning of benzene toxicity in the absence
						of other causative factors (most commonly infection). Likewise, the
						appearance of metamyelocytes, in the absence of another probable
						cause, is to be considered a possible indication of benzene-induced
						toxicity;
* An upward trend in the number of
						basophils, which normally do not exceed about 2.0 percent of the
						total white cells, is to be regarded as possible evidence of benzene
						toxicity. A rise in the eosinophil count is less specific but also
						may be suspicious of toxicity if it rises above 6.0 percent of the
						total white count;
* The normal range of monocytes is
						from 2.0 to 8.0 percent of the total white count with an average of
						about 5.0 percent. About 20 percent of individuals reported to have
						mild but persisting abnormalities caused by exposure to benzene show
						a persistent monocytosis. The findings of a monocyte count which
						persists at more than 10 to 12 percent of the normal white cell count
						(when the total count is normal) or persistence of an absolute
						monocyte count in excess of SOO/mm' should be regarded as a possible
						sign of benzene-induced toxicity;
* A less frequent but more serious
						indication of benzene toxicity is the finding in the peripheral blood
						of the so-called "pseudo" (or acquired) Pelger-Huet anomaly. In this
						anomaly many, or sometimes the majority, of the neutrophilic
						granulocytes possess two round nuclear segments - less often one or
						three round segments - rather than three normally elongated segments.
						When this anomaly is not hereditary, it is often but not invariably
						predictive of subsequent leukemia. However, only about two percent of
						patients who ultimately develop acute myelogenous leukemia show the
						acquired Pelger-Huet anomaly. Other tests that can be administered to
						investigate blood abnormalities are discussed below; however, such
						procedures should be undertaken by the hematologist.
2. Sucrose water test and Ham test:
* An uncommon sign, which cannot be
						detected from the smear, but can be elicited by a "sucrose wateriest"
						of peripheral blood, is transient paroxysmal nocturnal hemoglobinuria
						(PNH), which may first occur insidiously during a period of
						estabhshed aplastic anemia, and may be followed within one to a few
						years by the appearance of rapidly fatal acute myelogenous leukemia.
						Clinical detection of PNH, which occurs in only one or two percent of
						those destined to have acute myelogenous leukemia, may be difficult;
						if the "sucrose water test" is positive, the somewhat more definitive
						Ham test, also known as the acid-serum hemolysis test, may provide
						confirmation.
Important clinical
						findings
1. Individuals documented to have
						developed acute myelogenous leukemia years after initial exposure to
						benzene may have progressed through a prehminary phase of hematologic
						abnormality. In some instances pancytopenia (i.e., a lowering in the
						counts of all circulating blood cells of bone marrow origin, but not
						to the extent imphed by the term "aplastic anemia") preceded leukemia
						for many years.
* Depression of a single blood cell
						type or platelets may represent a harbinger of aplasia or leukemia.
						The finding of two or more cytopenias, or pancytopenia in a
						benzene-exposed individual, must be regarded as highly suspicious of
						more advanced although still reversible, toxicity.
* "Pancytopenia" coupled with the
						appearance of immature cells (myelocytes, myeloblasts,
						erythro-blasts, etc.), with abnormal cells (pseudo Pelger-Huet
						anomaly, atypical nuclear heterochromatin, etc.), or unexplained
						elevations of white blood cells must be regarded as evidence of
						benzene overexposure unless proved otherwise.
* Many severely aplastic patients
						manifested the ominous findings of:
- 5 to 10 % myeloblasts in the
						marrow;
- Occasional myeloblasts and
						myelocytes in the blood;
- 20 to 30 monocytes.
* It is evident that isolated
						cytopenias, pancytopenias, and even aplastic anemias induced by
						benzene may be reversible and complete recovery has been reported on
						cessation of exposure. However, since any of these abnormalities is
						serious, the employee must immediately be removed from any possible
						exposure to benzene vapor.
- Certain tests may substantiate
						the employee's prospects for progression or regression. One such test
						would be an examination of the bone marrow, but the decision to
						perform a bone marrow aspiration or needle biopsy is made by the
						hematologist.
2. The findings of basophilic stippling in
						  circulating red blood cells (usually found in one to five percent of
						  red cells following marrow injury), and detection in the bone marrow
						  of what are termed "ringed sideroblasts" must be taken seriously, as
						  they have been noted in recent years to be premonitory signs of
						  subsequent leukemia.
3. Recently peroxidase-staining of
						circulating or marrow neutrophil granulocytes, employing benzidine
						dihydrochloride, have revealed the disappearance of, or diminution
						in, peroxidase in a sizable proportion of the granulocytes, and this
						has been reported as an early sign of leukemia. However, relatively
						few patients have been studied to date. Granulocyte granules are
						normally strongly peroxidase positive. A steady decline in leukocyte
						alkaline phosphatase has also been reported as suggestive of early
						acute leukemia.
- Peroxidase and alkaline
						phosphatase staining are usually undertaken when the index of
						suspicion for leukemia is high.
4.Exposure to benzene may cause an
						early rise in serum iron, often but not always associated with a fall
						in the reticulocyte count. Thus, serial measurements of serum iron
						levels may provide a means of determining whether or not there is a
						trend representing sustained suppression of erythropoiesis.
5.Measurement of serum iron, determination of
						  peroxidase and of alkaline phosphatase activity in peripheral
						  granulocytes can be performed in most pathology laboratories.
Statutory Authority:
				  RCW  49.17.010,
				  49.17.040,
				  49.17.050,
				  49.17.060. 07-03-153,
				  § 296-849-60020, filed 1/23/07, effective
				  6/1/07.