BARIUM and COMPOUNDS

Barium Carbonate News


BARIUM and COMPOUNDS / Toxicology

Section: Materials, Subsection: Safety

Description

BARIUM and COMPOUNDS / Toxicology - Edouard Bastarache

Article

Compounds:

 

The main water soluble saltsare:theacetate, chloride, hydroxide, oxide, nitrate.

The main insoluble salts are:thearsenate,carbonate, chromate, fluoride,oxalate,sulphate.

 

Uses :

 

-Rodenticide,insecticide,fungicide

-Manufacture of glass

-Manufacture of ceramics

-Vulcanization of synthetic rubber

-Production of pigments

-Manufactureofelectroniccomponents

-Manufacture ofdetergentsforlubricatingoils

-Purification of industrial waters

-Industry of painting

-Industry of paper

-In pottery

-Coating of welding electrodes

-Surface treatmentinthemetallurgicalindustry

-Barium sulphide is usedintheproductionof certain types of fluorescent tubes

-Barium sulphate isusedinmedicalradiology and in the manufactureofwhitepigments(litophone)

-Etc.

 

Exposure :

 

1-Environmental :

 

Barium naturallyoccursatlowconcentrations in ambient air, usually < 0.05µg/m3,butisfound at relatively high concentrations in soils,nearly500mg/kg. In fresh surface water, concentrations mayvaryfrom <5to 15,000 µg/L. and it contributes towaterhardness.Foodstuffsprovide also barium and the daily humanintakehas beenestimatedto be in the order of 1 mg.

 

2-Industrial :

 

The pulmonary route of entryisthemostsignificant in the industrial setting(seeexposurelimitrecommendations).

 

Routesofentry:

 

Soluble barium salts arewellabsorbedbypulmonary and oral routes of entry.

Insoluble salts inhaledanddepositedareeliminated only slowly and can accumulate in thelungsas aresultof long-term exposure. Barium compounds arenotreputedtopenetrate by skin unless the cutaneous barrier isbrokenasinchemical burns; a case has been described intherelevantmedicalliterature which had been caused bybariumchlorideinfusion.

 

Toxicity :

 

1 - Solubility :

 

The toxicity of bariumsaltsisrelatedlargely to their solubility, whichconditionstheirdigestiveabsorption and bioavailability. Water andacidsolublesalts arevery toxic when ingested.

 

The carbonate BaCO3 is insolubleinwateratneutral pH, it becomes soluble in acid environments,whichisnotwithout consequence in vivo because of the gastricpH.Therewould beunder this condition, production of bariumchlorideBaCl2from thesolubilized carbonate; barium chloride is onethemosttoxic ofsoluble barium salts.

 

2 - Metabolism :

 

The biological half-lifeofbariumvariesbetween 2 and 20 hours. Absorbed barium ismainlydepositedinbones, which accounts for 93% of the body burdenin man.Itismainly excreted in feces and a small part (1to10%)inurine.

 

3 - Exprimental toxicity :

 

In the case of bariumcarbonate,theLethalDose Fifty (LD50) is :

-mouse (ingestion): 200 mg/kg,

-rat (ingestion): 418 mg/kg,

which makes it a verytoxicchemicalbyingestion.

 

Barium stimulates thestriatedandcardiacmuscles. This hyperstimulationcausesarrhythmias,myoclonus,digestive disorders and arterialhypertensionby directeffect onthe smooth muscles of the arterialwallindependently oftherenin-angiotensin systemandcatecolamines.

 

4 - Acuteintoxicationbyingestion:

 

The lethal dose in manvaries,accordingtobarium compounds involved, between 1 and 15 g.byingestion.Acuteintoxications are rare and generally duetosuicidal attemptswiththe chloride or the carbonate.

 

Some cases ofcollectivefoodintoxicationswere reported, related to foodcontamination, andtoconfusionbetween carbonate and barium sulphateat the timeofradiologicalexaminations. Barium carbonate havingbeensubstitutedaccidentallyfor potato flour during the preparationofsausages,144 people werepoisoned in Israel in 1963.Twopatientsdied.

 

A - Clinical findings :

 

At the beginning,therearedigestivedisorders :

 

-diarrhoea, sometimes hemorrhagic,

-severe abdominal pain,

-nausea and vomiting.

 

Initially thereisintenseasthenia,sometimes accompanied by :

 

-muscle cramps,

-myoclonus,

-muscular contractures.

 

Later there is :

 

-graduallyincreasingflaccidparalysisinvolving the 4 limbs, the diaphragm,andthepharyngolaryngealjunction, which often requires toresorttoartificialventilation.

-the clinical picture maymimickarapidlyevolving Guillain-Barré's syndrome

-respiratorydisordersandrhabdomyolysiswere reported.

 

Cardiac symptoms andclinicalsignsdominatethe prognosis :

 

-Initially therecanbearterialhypertension sometimes followed by hypotensionduetodigestiveliquid losses (diarrhoea, vomiting).

-Disordersofexcitabilityandconduction,

-Ventricular tachycardia,

-Torsades de pointes ("twistingofthepoints ") leading sometimes toanunexpectedventricularfibrillation responsible for the fataltypesoftheintoxication.

 

Renal complications werereportedinanexceptional manner :

 

-Acute kidneyfailurewithpreserveddiuresis,

-Opacification of kidneysduetobariumprecipitation.

 

Death occurs byrespiratoryfailureorventricular fibrillation.

 

B - Laboratory findings :

 

-Biologicalexaminationshighlightdisorders related to water losscausedbydiarrhoea.

- Hypokaliemia (lowlevelsofbloodpotassium) sometimes very significantwithacidosis,ischaracteristic of the intoxication. However,initiallyit canbemasked by respiratory acidosis.

-Electrocardiographicchangesreflectcardiac effects

-When the blood concentrationofbariumwasmeasured in the course of acute intoxications,valuesgreaterthan100 µg/L were observed. However, bloodconcentrationsfallquicklyduring the first 48 hours to become againlowerthan10µg/L.

- As renal clearance of bariumisrapid,theduration of the intoxication lasts 2 to 4 days.

 

 

C - Treatment :

 
It comprisesusualsymptomaticmeasures:

 

-Gastric lavage,rehydrationandcorrectionof hydroelectrolytic imbalance.

-Oral magnesium sulphate(Epsomsalt)orsodium sulphate makes it possible toprecipitatesolublebariumsalts present in the digestive tractasbariumsulphate(insoluble).

Perfusion of the samesaltsbyintravenousroute could cause renal complications,byintratubularprecipitationof barium.

-Perfusion of importantamountsofpotassiumis often necessary to correct hypokaliemiamainly duetodisorders ofpotassium membrane transfer, which arecorrectedonlyby theelimination of circulating barium.

- Treatment ofcardiacdisordersissymptomatic.

 

 

5 - Pulmonary effects :

 

Handling of pulverulentbariumsulphatewasaccompanied, at the time of already oldobservations,bybenignpneumonias generally resulting inpulmonaryradiologicalimagesconsisting of nodules disseminated inboth lungfieldswithoutclinical symptoms, nor anomalies ofrespiratoryfunctionaltests,it is barytosis.

It also occursduringsignificantexposuresto lithophone and barium oxide.

 

On the other hand,seriousfibrosiswasreported among workers of barium mines because ofthepresenceofcrystaline silica in the ore.

 

Aqueous solutions ofbariumhydroxideandoxide are strongly alkaline and can causesignificantocularburnsand skin irritation. The carbonate and thesulphate ofbariumareirritating to the mucous membranes of theupperairways,thecarbonate can also be irritating to the skinandtheeyes.

 

6 - Local effects :

 

Aqueous solutions ofbariumhydroxideandoxide are strongly alkaline and can causesignificantocularburnsand skin irritation. The carbonate and thesulphate ofbariumareirritating to the mucous membranes of theupperairways,thecarbonate can also be irritating to the skinandtheeyes.

 

Carcinogenesis:

 

Barium chromate(VI) istheonlycompoundrecognized as carcinogenic in man.

 

Mutagenesis:

 

Barium chloride dihydratewasnotmutagenicin Salmonella typhimurium, nor did itinducesisterchromatidexchanges or chromosomal aberrations inculturedChinesehamsterovary cells.

 

Developmentaleffects:

 

In a mating trial,noadverseanatomicaleffects were observed in the offspring of ratsormicereceiving upto 4000 ppm barium chloride dihydrate inthedrinkingwater,although rat pup weight was reduced.

 

Reproduction:

 

In rats and mice receiving upto4000ppmbarium chloride dihydrate in thedrinkingwater,reproductiveindices were unaffected.

 

Exposurelimitrecommendations :

 

The TLV-TWA (ACGIH) forsolublebariumsaltsis 0.5 mg/m3. The TLV for barium sulphatedust(insoluble) is10mg/m3.

 

Prevention:

 

Good housekeeping ofyourstudioisimportant as for any other chemical.

Avoidanceofprocessesgeneratingunnecessary dust is also important.

Depending on the severityofexposure,localventilation should be used and the aspiredairshould beventedoutside to avoid producing dust from worktablesand thefloor.

 

Very effective filter masksshouldbewornif the severity of exposure justifies itduringpreparationofglazes and clays.

 

It should be forbidden todrink,eatorsmoke in the workshop.

 

Especially, one shouldnotconfusebariumcarbonate with table sugar whenpreparingcoffee.

 

Medicalsurveillance:

 

An electrocardiogram isrecommendedaspartof the periodical examination of workers exposedtosolublesalts.Periodical urinary and blood mesurements couldalsobecarried out;in subjects not professionallyexposedbloodconcentrations are lowerthan 10 µg/L, and lower than20µg/Lin theurine

EdouardBastaracheM.D.(Occupational& Environmental Medicine)

Author of "Substitutions for raw ceramic materials"

Authors

• EDOUARD BASTARACHE (Owner)

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