UK Government Information

Notes on the Diagnosis of Prescribed Diseases

CONDITIONS DUE TO CHEMICAL AGENT

DISEASE C7

POISONING BY BENZENE or a homologue of benzene

SCHEDULED OCCUPATION

Any occupation involving the use or handling of, or exposure to the
fumes of, or vapour containing Benzene or any of its homologues.

CAUSATIVE AGENT 1 Benzene. C6H6. A colourless, freely volatile solvent with a distinctive odour.

CAUTION: Benzine is not the same as Benzene. Benzene is an aromatic hydrocarbon, whereas Benzine is a mixture of essentially aliphatic hydrocarbons, and is much less toxic. It is also used as a solvent.

HARMFUL EFECTS.

1. Narcotic and irritant.
2. Bone marrow depressant.

TYPES OF WORK INVOLVED.

Benzene is the basic aromatic carbon ring structure and is the starting point for the synthesis of a whole range of ring based chemicals.

ENVIRONMENTAL LIMITS.

Published occupational exposure standards have been chosen in the expectation that no-one subjected to them will suffer harm. The limits cannot take into account individual susceptibility and exposure to permitted levels does not necessarily rule out a diagnosis of poisoning.

Exposure limit levels are constantly being revised. The figures quoted below are intended only as a guide. For full details please consult the Health and Safety Executive, Magdalen House, Stanley Precinct, Bootle, Merseyside L20 3QZ.

Recommended maximum time weighted average concentrations.
These are to be reviewed soon by the Advisory Committee on Toxic Substances.

For an 8 hour day/ 40 Hour week 10 ppm = 3mgm/m3

BIOLOGICAL MONITORING.

Urinary phenol excretion is a non-specific marker for benzene exposure. Phenol is normally present in the urine and this has been taken into account in setting an acceptable maximum limit. Whether or not any particular phenol level signifies exposure to benzene sufficient to cause poisoning depends on individual susceptibility. As with environmental limits biological indices are subject to revision and full details should be sought from the HSE.

Maximum recommended urine phenol concentration 50 mgm/litre

The measurement must be made immediately after a shift with a urine Specific gravity of 1.010 or more and a creatinine clearance of 0,5g/l or more.

Benzene can be detected in expired air. Interpretation of results is difficult and the figures are only intended to show what might be expected from exposure to maximum environmental levels.
Measurements should be made just before a shift.

Maximum recommended concentration

In mixed exhaled air 0.08 ppm
In end exhaled air 0.12 ppm

SAFE WORKING PRACTICE.

Benzene should only be used in sealed systems and any chance of exposure kept to a minimum by efficient ventilation. A diagnosis of poisoning implies either that the exposure/biological limits are too high for the particular claimant or that there has been a failure of exposure control.

DIAGNOSIS - ACUTE

History.

Inadvertent exposure to benzene fumes at a concentration higher than the recommended limits.

Symptoms

Burning soreness of the skin. Dizziness, tightening of the leg muscles, pressure over forehead, excitement, stupefaction and coma.

Signs

Redness, swelling and blistering. Compatible with the anaesthetic action of benzene.

Investigation As appropriate.

DIAGNOSIS CHRONIC

History.

Exposure to benzene at or about the recommended limit with possible intermittent exposure to higher levels.

Symptoms.

These come on slowly and are vague. Fatigue, headache, dizziness, nausea, loss of appetite and weight, weakness, nose bleeds and, in women, menorrhagia.

Signs

Pallor, petechiae and purpura.

Investigation

Appropriate to the elucidation of chronic bone marrow disease including leukaemia. These diseases are no different from bone marrow disease not due to benzene poisoning.

SPECIAL POINTS

The early symptoms of chronic benzene poisoning are common and non-specific. In modern plant there is likely to be very little benzene. Only after careful consideration of all the facts including, where possible, data from the factory should symptoms be attributed, on the balance of probability, to the action of benzene.

A single large accidental exposure to benzene may give rise to a short period of poisoning. Particular care should be taken to state the duration of symptoms and signs and whether or not any long-term sequelae are to be expected.

CAUSATIVE AGENT 2

Toluene C6H5(CH3) a homologue of benzene. A colourless liquid with a smell reminiscent of benzene.

HARMFUL EFFECTS

Anaesthetic.

TYPES OF WORK INVOLVED

Toluene is an important raw material in the chemical industry where it is used to synthesize other compounds. It is very widely used as a sollvent for oils, resins, rubber, tar, asphalt, acetyl cellulose, cellulose paints and varnishes. It is a cleaning agent.

ENVIRONMENTAL LIMITS

Occupational Exposure Standard (Time Weighted Average)concentrations :

For an 8 hour day/40 hour week 100 ppm = 375 mgm/m3

For no more than 10 minutes (STEL) 150 ppm = 560 mgm/m3

BIOLOGICAL MONITORING

Toluene absorption shows as urinary hippuric acid excretion.
Measurement may be of the concentration in a sample at the end of a shift or of the rate of excretion over a 4 hour period.

Maximum values

End of shift sample 2.5 g/g creatinine

Rate for last 4 hours of a shift 3.0 mgm/min

Toluene itself may be measured in venous blood or end exhaled air

Blood, end of shift 1.0 mgm/litre

Air, during shift 20 ppm

DIAGNOSIS - ACUTE

History

Exposure to toluene vapour at concentrations above the recommended limits.

Symptoms

Irritation of the mucous membranes, vertigo, difficulty in keeping the balance, intense frontal headache, coma and respiratory depression.

Signs

Consistent with the narcotic action of toluene.

Investigation

As appropriate.

DIAGNOSIS CHRONIC

History

Exposure to toluene vapour at or about the recommended limit with possible intermittent exposure to higher concentrations.

Symptoms

Irritations of the mucous membranes, euphoria, headaches, vertigo, nausea, loss of appetite and alcohol intolerance. Symptoms are worse at the end of the day and remit at weekends.

Signs

Usually absent.

Investigation

About 68 per cent of absorbed toluene is converted by the liver into hippuric acid and this is the basis for the biological exposure indices quoted above. Hippuric acid is also an ingredient of fruit and vegetables.

SPECIAL POINTS

Toluene has no effect on the bone marrow. If there is bone marrow toxicity it is probably due to the presence of benzene as a constituent or contaminant.

CAUSATIVE AGENT 3

Xylene C6H4(CH3)2 A homologue of benzene. A colourless liquid with an aromatic odour.

HARMFUL EFFECTS

A narcotic.

TYPES OF WORK INVOLVED

Xylene is a thinner for paints, varnishes and mastics. It is used in the synthesis of pharmaceuticals, dyes and chemicals and as an additive to aviation fuels. Histologists use it as a clearing agent.

ENVIRONMENTAL LIMITS

Occupational Exposure Standard (Time Weighted Average) concentrations:

For an 8 hour day/40 hour a week 100 ppm = 435 mgm/m3

For no more than 10 minutes (STEL) 150 ppm = 650 mgm/m3

BIOLOGICAL MONITORING

Absorbed Xylene is excreted as methylhippuric acids

Maximum values

End of shift sample 1.5 g/g creatinine

Rate for last 4 hours 2.0 mgm/min

DIAGNOSIS ACUTE

History

Exposure to xylene vapour at greater than the recommended concentrations.

Symptoms

Fatigue, dizziness, drunkenness, shivering, dyspnoea, nausea, vomiting, coma and respiratory depression. Irritation of the eyes and nasal mucosa.

Signs

Appropriate to the symptoms.

Investigation

Not applicable.

DIAGNOSIS - CHRONIC

History

Exposure to xylene fumes at or about the recommended limit with possible occasional exposure to higher concentrations.

Symptoms

General weakness, fatigue, dizziness, headaches, irritability, Sleeplessness, loss of memory, ringing in the ears, a sweet taste in the mouth, nausea, loss of appetite, thirst, and irritation of the mucous membranes.

Signs

Eczematous rash, pallor and other signs indicative of bone marrow dysfunction.

Investigation

Aimed at revealing bone marrow poisoning leading to changes in the peripheral blood. Xylene is said not to cause leukaemia.

DUE TO THE NATURE OF

When a Prescribed Disease is diagnosed in a worker who is
  1. currently employed in or;
  2. within a month of having left the relevant scheduled occupation, the disease should be presumed to be due to the nature of the occupation unless there is evidence to the contrary. The claimant might have a hobby which uses paint thinners or solvents and there is the possibility of substance abuse.

 Outside those time limits each case should be considered on its merits and the evidence weighed before expressing an opinion on whether or not the condition was due to the nature of the claimant’s work.

SPECIAL POINTS

Industrial solvents may contain mixtures of benzene and its homologues. Where benzene is present this is the most toxic part and poisoning is likely to be due to it. The industrial mixtures may be called Benzol, Toluol or Xylol. They are readily available and easily abused so a claimant who is sufficiently exposed at work to satisfy the occupational requirements may also be exposed to higher doses at home.

DISEASE C8

POISONING BY A NITRO OR AMINO OR CHLORO-DERIVATIVE OF BENZENE or a homologue of benzene, or poisoning by nitrochlorbenzene

SCHEDULED OCCUPATION

Any occupation involving the use or handling of, or exposure to the fumes of,or vapour containing a nitro- or amino- or chloro-derivative of benzene, or of a homologue of benzene or nitro-chlorbenzene.

CAUSATIVE AGENT

Nitro derivatives

Benzene, mononitrate, dinitrate, trinitrate

Toluene, nitrotoluene, dinitrotoluene, trinitrotoluene

Xylene, trinitroxylene

Amino derivatives

The nomenclature is complex. Each substance may have several names. Amino benzene is, for example, aniline. The addition of other radicals to the aniline molecule gives a range of compounds which are related both to aniline and benzene. Their names may be derives from either aniline or the more distant benzene root. For simplicity aniline related names are given below with other common synonyms where appropriate. For further details please consult a specialist text (eg, Dangerous Properties of Industrial Materials, N Irving Sax, 6th edition, Van Nostrand Reinhold Company, New York, Toronto, London, Melbourne, ISBN 0 442 28304 0, 1984.)

Benzene Amino aniline (phenylenediamine)

Methylaniline (toluidine)

Dimethylaniline (xylidine)

Ethylaniline

Diethylaniline

Phenylaniline (Diphenylamine)

Nitroaniline

Dinitroaniline

Toluene Toluidine, see methylaniline

Xylene Xylidine, see dimethyaniline

Chloro derivatives

Benzene Monochlorbenzene

Dichlorbenzene

Paradichlorbenzene

Nitrochlorbenzene

HARMFUL EFFECTS

Most of the substances listed have one or more of these harmful effects. Severity depends on the particular substance under consideration.
  1. Direct nervous system toxicity, an anaesthetic like effect.
  2. Methaemoglobinaemia formation which impairs the oxygen carrying capacity of the blood.
  3. Haemolytic effects.
  4. Bone marrow depression.
  5. Irritation of the skin and epithelial lining of the respiratory and gastro intestinal systems.
  6. Allergic effects.
  7. Carcinogenic effects, especially of the urinary tract.

TYPES OF WORK INVOLVED

Production of chemicals, dyes, explosives, solvents, lacquers, disinfectants, fumigants and wood preservatives.

ENVIRONMENTAL LIMITS

Published occupational exposure standards have been chosen in the expectation that no-one subjected to them will suffer harm. The limits cannot take into account individual susceptibility and exposure to permitted levels does not necessarily rule out a diagnosis of poisoning.

Exposure limit levels are constantly being revised. For full details of recommended maximum time weighted average concentrations please consult the appropriate Health and Safety Executive publications:

Health and Safety Executive, Magdalen House,Stanley Precinct,Bootle, Merseyside L20 3QZ

BIOLOGICAL MONITORING

Aniline and other substances are excreted as para-aminophenol in urine. Its measurement is not specific aniline but a raised level may indicate there has been aniline absorption.

Recommended maximum urinary level 50 mgm/litre

The descriptions of poisoning which follow are based on clinical experience dating from days when environmental exposure limits were either non-existent or higher than they are now. Industrial exposure to no more than the quoted levels is expected to have no ill effects so a diagnosis of poisoning implies either that the exposure limits are too high for the particular claimant or that there has been a failure of exposure control and/or biological monitoring.

DIAGNOSIS - ACUTE

History

Uptake of the relevant chemical by inhalation, ingestion or absorption through the skin, particularly from splashed clothing.
Toxicity is related not only to the substance involved but also to its physical state. Liquids and vapours are more readily absorbed than solids.

Symptoms

These are related to the known harmful effects of the chemicals.

  1. CNS poison. As for any intoxicant.
  2. Methaemoglobin formation. The symptoms are due to gradually increasing anoxia
    Headache
    Weakness
    Malaise
    Confusion
  3. Skin irritation ) as for any other similar agent
  4. Allergic effects )as for any other similar agent

Signs

  • As for any other intoxicant.
  • Cyanosis is apparent at a methaemoglobin level of 10 per cent of Total haemoglobin. Other signs are as for progressive anoxia.
    •

    Appropriate to the acute clinical condition.

    DIAGNOSIS - CHRONIC

    History

    Exposure levels of the toxic agents at or about the recommended limits with possible intermittent exposure to higher levels.

    Symptoms

    The symptoms and signs of exposure to low levels of these toxic agents are non-specific. Occasionally claimants may have unrelated diseases which they attribute to chemicals at work. In such cases the symptoms and signs will be of the diseases.

    Harmful effects

    Symptoms & Signs
    CNS toxicity.  Usually only related to monochlor-benzene headaches, stupor, difficulty with micturition.
    Methaemoglobinaemia.  Methaemoglobinaemia is normally present in blood at a concentration of 1-2 per cent of total haemoglobin. A rise to 10-15 percent is usually more apparent to an observer than to the victim. Cyanosis of the oral mucosa is usually apparent at this level.
    Haemolysis.  Symptoms may be absent or non-specific.There may be clinical anaemia, with signs of haemolytic jaundice.
    Bone marrow depression.   Usually first detected by blood tests.
    Irritation.  Aminoalinine is a potent cause of contact dermatitis.
    Trinitrotoluene causes a toxic gastritis and hepatitis which gives rise to symptoms and signs appropriate to liver damage.
    Allergen.  As for any other allergen.
    Carcinogen.  Growths of the uroepithelium are a separate prescribed disease, C23.

    Investigation

    This will usually be directed to discovering whether or not there has been
  • Significant absorption of the chemical concerned;
  • If so, whether or not it is responsible for the claimant’s condition. The fact that someone works in a scheduled occupation does not imply that he has been exposed to large quantities of chemical. The occupational test may be satisfied in people whose work brings them into contact with minute quantities of the relevant agent.
    •

    DUE TO THE NATURE OF

    When a Prescribed Disease is diagnosed in a worker who is:
  • a.currently employed in or;
  • b. within a month of having left the relevant scheduled occupation, the disease should be presumed to be due to the nature of the occupation unless there is evidence to the contrary. Outside those time limits each case should be considered on its merits and the evidence weighed before expressing and opinion as to whether or not the condition was due to the nature of the claimant’s work.
    •

    SPECIAL POINTS

    The early symptoms and signs of poisoning are not clear cut. It is important to pay special attention to the degree of exposure before deciding whether, on balance, any particular clinical findings represent poisoning by one of the relevant chemicals.

    A single accidental exposure to high concentrations of any of the agents may result in temporary poisoning. In that case please state clearly the duration of symptoms and signs and whether or not any long-term sequelae are to be expected.
    The full paper ISBN 1 85197 770 8 may be difficult to obtain.

    Dated 16/9/2000

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