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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Absorption rate - oral (%):
Absorption rate - dermal (%):
Absorption rate - inhalation (%):

Additional information

Valence, speciation and other general or mechanistic aspects


Changes in valence of “barium” do not occur under physiological conditions and are therefore not relevant.


Inorganic sulfides or hydrogensulfides as well as H2S will dissociate to the respective species relevant to the pH of the physiological medium, irrespective of the nature of the “sulfide”, which is why read-across between these substances and H2S is considered to be appropriate without any restrictions for the purpose of hazard and risk assessment of barium sulfide. Speciation of sulfides and hydrogen sulfides may be considered to be of relevance when relating toxicity to bioavailability.


However, taking into account the reaction of sulfide and hydrogen sulfide in aqueous media (please refer to the Hägg graph given in IUCLID section 5.1.2 Hydrolysis), it can safely be assumed that under most physiologically relevant conditions (i.e., neutral pH) sulfide and hydrogen sulfide anions are present at almost equimolar concentrations, thus facilitating unrestricted read-across between both species. Under extreme conditions such as gastric juice (pH << 2), sulfides will be present predominantly in the form of the undissociated hydrogen sulfide.


Oral absorption


There are only few publications that allow an assessment of the oral bioavailability of sulfide in rats, which are also somewhat of age. Nevertheless, the following conclusions can be drawn: after oral administration of sulfide to rats (Curtis et al., 1972) almost 70% are excreted within 48 hrs, 63% via urine and the remainder via faeces. In another study involving intraperitoneal administration, 90% of the injected dose could be recovered in urine and faeces (Dziewiatkowski, 1945).In conclusion, the assumption appears justified that upon oral uptake the systemic uptake is essentially complete for sulfides and hydrogen sulfides. Therefore, a conservative oral absorption factor of 100% will be taken forward for risk characterisation purposes.

For more details please refer to the attachment on section 7.


A thorough evaluation by a renowned scientific body is available (ATSDR, August 2007), the key conclusions of which are summarised briefly below:


“The absorption of barium from the gastrointestinal tract is compound dependent. Barium sulfate is extremely insoluble and very little, if any, ingested barium sulfate is absorbed. Acid-soluble barium substances, such as barium chloride and barium carbonate, are absorbed through the gastrointestinal tract, although the amount of barium absorbed is highly variable. Older human studies estimated that barium was poorly absorbed; approximately 1–15% of the ingested dose was estimated to be absorbed (Harrison et al. 1956; LeRoy et al. 1966; Schroeder et al. 1972; Tipton et al. 1969). A re-examination of the methods used in these studies found a number of flaws; Leggett (1992) estimated that barium absorption in these studies was approximately 3–60%.Studies in adult rats and dogs estimated fractional absorption at 7%(Cuddihy and Griffith 1972; Taylor et al. 1962). Several unpublished animal studies discussed by Leggett (1992) found absorption rates of 1–50%. Experiments in rats have shown that younger animals (22 days old or less) absorb about 10 times more barium chloride from the gastrointestinal tract (63–84%) than do older animals (about 7%) (Taylor et al. 1962).Absorption was higher in fasted adult rats (20%) as compared to fed rats (7%).The International Commission for Radiation Protection (ICRP) estimates that the gastrointestinal absorption of barium is 20% in adults, 30% for children aged 1–15 years, and 60% in infants (ICRP 1993).”

Based on the above described weight-of-evidence approach by ICRP (1993), human oral absorption factors of 20% (adults), 30% (children 1-15 yrs) and 60% (infants) were selected as the most relevant for the hazard assessment of barium compounds for systemic effects. For reference purposes with animal data, an oral absorption factor of 7% was chosen based on the studies by Taylor et al.(1962).

Dermal absorption (barium sulfide)

In the absence of measured data on dermal absorption, current guidance suggests the assignment of either 10% or 100% default dermal absorption rates. In contrast, the currently available scientific evidence on dermal absorption of metals (predominantly based on the experience from previous EU risk assessments) yields substantially lower figures, which can be summarised briefly as follows:


Measured dermal absorption values for metals or metal substances in studies corresponding to the most recent OECD test guidelines are typically 1 % or even less. Therefore, the use of a 10 % default absorption factor is not scientifically supported for metals. This is corroborated by conclusions from previous EU risk assessments (Ni, Cd, Zn), which have derived dermal absorption rates of 2 % or far less (but with considerable methodical deviations from existing OECD methods) fromliquidmedia.


However, considering that under industrial circumstances many applications involve handling of dry powders, substances and materials, and since dissolution is a key prerequisite for any percutaneous absorption, a factor 10 lower default absorption factor may be assigned to such “dry” scenarios where handling of the product does not entail use of aqueous or other liquid media. This approach was taken in the in the EU RA on zinc. A reasoning for this is described in detail elsewhere (Cherrie and Robertson, 1995), based on the argument that dermal uptake is dependent on the concentration of the material on the skin surface rather than it’s mass.

Consistent with the methodology proposed in HERAG guidance for metals (HERAG fact sheet - assessment of occupational dermal exposure and dermal absorption for metal cations and inorganic metal substances; EBRC Consulting GmbH / Hannover /Germany; August 2007), the following default dermal absorption factors for metal cations have therefore been proposed (reflective of full-shift exposure, i.e. 8 hours):


From exposure to liquid/wet media:                    1.0 %

From dry (dust) exposure:                                  0.1 %


Given that the primary cause between the lack of percutaneous transfer is considered to be the ionic nature, it is proposed to assume similar behaviour for sulfides anions as for metal cations, and to adopt the above stated dermal absorption factors for barium sulfide. 

Inhalation absorption (barium sulfide)

The systemic availability of different barium substances via the inhalation route can be expected as a function of regional deposition in the respiratory tract, which in turn depends foremost on the particle size distribution of the inhaled dust. However, product-specific physical particle size distributions do not necessarily reflect the particle size of aerosols that may be formed under practically relevant workplace conditions, for example during manual operations such as filling and emptying of bags, or under mechanical agitation as in mixing and weighing operations.


Barium sulfide was subjected to an experimental testing programme. The physical particle size distribution of the commercial material was determined by laser diffraction (acc. OECD 110) and is represented by the median particle size diameter D50.


In addition, to simulate mechanical agitation, the sample was introduced into a rotating drum apparatus according to DIN 55992 Part 1. In this modified rotating drum method, a fraction of the material becomes airborne and is carried out of the drum by a constant air stream into a cascade impactor. From the mass fractions deposited on the impactor stages, the mass median aerodynamic diameter (MMAD) of the airborne material has been determined together with the geometric standard deviation (GSD) of the MMAD (EBRC Report: EBR-20130807/01).


In the absence of actual measurements of the distribution of dust particles in the workplace air, the above determined MMAD and GSD can therefore be used as surrogate parameters of the associated particle size distribution.


It takes into account potential particle agglomeration under mechanical agitation and the fact that larger/heavier particles show less tendency to become airborne (and are therefore not likely to be available via inhalation of workplace air).


The relative density of the sample was taken of different handbooks, which could be seen as reliable data under REACH. However, the methods used were not stated. Data on particle size, relative density and calculated MMAD and associated GSD are presented in following table:



Table: Data on particle size, dustiness and relative density of barium sulfide (EBRC Report: EBR-20130807/01)

Test item

relative density



MMAD of airborne particles


Geometric standard deviation of MMAD

Barium sulfide

4.3 at 20°C




*d50 = median physical particle size

#MMAD = mass median aerodynamic diameter


In order to estimate the deposition in the respiratory tract (head, tracheobronchial and pulmonary region) of particles the Multiple Path Particle Deposition (MPPD) model (CIIT, 2002-2006) was used with the following input data; The human–five lobular lung model, a polydisperse particle distribution, oronasal (normal augmenter) mode, a full shift breathing volume of3- corresponding to a tidal volume of 1042 ml and a breathing frequency of 20 breaths * min-1, and an aerosol concentration of 500 µg/m3.


Table: Calculated deposited fractions of barium sulfide (EBRC report no.: EBR-20130807/01).

Test item

Head [%]

TB [%]

PU [%]

Barium sulfide





Based on the MPPD model, the following conclusions can be drawn for risk characterisation purposes for barium sulfide:


(i)     the tested “Barium sulfide” sample has a limited deposition ability in the human respiratory tract: Only 48.3 % of airborne material is estimated to deposit. The rest of the airborne material is not inhaled due to physical phenomena related to air streams and turbulences close to the mouth or simply exhaled (i.e. not deposited).


(ii)    about 0.01 % or less of inhaled material are predicted to deposit in the pulmonary region (PU), whereas the material deposited in the tracheobronchial (TB) and the extrathoracic region (Head) may be assumed to be cleared to the GI tract (i.e., by mucociliary escalation and subsequent swallowing).


The fate and uptake of deposited particles depends on the clearance mechanisms present in the different parts of the airways of the respiratory tract.. In the head region, most material will be cleared rapidly, either by expulsion or by translocation to the gastrointestinal tract. A small fraction will be subjected to more prolonged retention, which can result in direct local absorption. More or less the same is true for the tracheobronchial region, where the largest part of the deposited material will be cleared to the pharynx (mainly by mucociliary clearance) followed by clearance to the gastrointestinal tract, and only a small fraction will be retained (ICRP, 1994). Once translocated to the gastrointestinal tract, the uptake will be in accordance with oral uptake kinetics.


In consequence, the material deposited in the head and tracheobronchial regions would be translocated to the gastrointestinal tract where it would be subject to gastrointestinal uptake at a ratio of 20% (see oral absorption). The material that is deposited in the pulmonary region may be assumed by default to be absorbed to 100%. This absorption value is chosen in the absence of relevant scientific data regarding alveolar absorption although knowing that this is a conservative choice. Thus, the following predicted inhalation absorption factor can be derived for barium sulfide (calculation details given in the following table):


Table: Absorption factors, barium sulfide


absorption factors*
via inhalation [%]

Test item

Barium sulfide


*: rounded values

Distribution, metabolism and elimination


Following oral administration, sulfides are absorbed rapidly and extensively, and distributed widely throughout all tissues without any particular target tissue (Curtis et al., 1972; Dziewiatkowski, 1945). Upon distribution, sulfide is rapidly oxidised and excreted as sulfate, with thiosulfate having been identified as an intermediate metabolite (Bartholomew et al., 1980). The resulting sulfate is excreted almost quantitatively via urine; experiments with bile duct cannulated rats have shown that biliary excretion is minimal by comparison (Curtis et al., 1972). Methylation with subsequent elimination via exhaled air has been excluded for sulfides (Susman et al., 1978).



Distribution: Following ingestion, in human barium is predominantly found in bone: approximately 90% of the barium in the body was detected in the bone. Approximately 1–2% of the total body burden was found in muscle, adipose, skin, and connective tissue. This information is supported by a number of studies. Significant increases in the levels of barium in bone were found in rats administered barium chloride in the diet or barium as a component of Brazil nuts for 29 days, although this study did not examine other tissues. A study in which rats were exposed to barium chloride and barium carbonate in drinking water found the following non-skeletal distribution (skeletal tissue was not examined in the study) 24 hours after ingestion: heart > eye > skeletal muscle > kidney > blood > liver (ATSDR, 2007).


Metabolism: Barium is not metabolised in the body, but it may be transported or incorporated into complexes or tissues (ATSDR, 2007).


Elimination: A study in two humans ingesting a normal diet found that fecal excretion of barium was 2–3 times higher than urinary excretion over a 30-day period. A 29-day rat study also demonstrated that the faeces was the primary route of excretion following exposure to barium chloride in the diet or barium from brazil nuts. A study in rats found that biliary excretion did not significantly contribute to the total amount of barium excreted in the faeces (Edel et al. 1991). In a study in rabbits administered an intravenous injection of radiolabelled barium, barium was primarily excreted in the faeces. After the first day, faecal excretion was approximately twice as high as urinary excretion. Barium was primarily excreted in the first 5 days after exposure; after 9 days, approximately 50% of the dose was excreted (ATSDR, 2007).