Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Base fluid

Poly alpha olefin (PAO)

Poly alpha olefins are of low acute toxicity and are not irritating to eye and skin.

Esters

Data on C8-C16 fatty acid 2-ethyl hexanol ester indicate that this ester is of low oral acute toxicity. In an acute skin irritation test in rabbits, minimal skin irritation was observed. The ester is not primarily eye irritant.

The ester was non-genotoxic in a micronucleus test. Results from an oral repeated dose study in rats indicate that the ester is not toxic at up to 1000 mg/kg.

Water

Fresh water

Fresh water is generally considered to be not hazardous to human health.

Sea water

Sea water has a low hazard potential for human health upon inhalation and dermal exposure.

Brine (see salts)

See Table 2 in Appendix 6, and below (osmotic—salts)

Osmotic—salts

Calcium chloride (CaCl2)

The acute oral and dermal toxicity of calcium chloride is low. The acute oral toxicity is attributed to the severe irritating property of the original substance or its high-concentration solutions to the gastrointestinal tract. In humans, however, acute oral toxicity is rare because large single doses induce nausea and vomiting. Irritation/corrosiveness studies indicate that calcium chloride is not/slightly irritating to skin but severely irritating to eyes of rabbits. Prolonged exposure and application of moistened material or concentrated solutions resulted in considerable skin irritation. The irritating effect of the substance was observed in human skin injuries caused by incidental contact with the substance or its high-concentration solutions. A limited oral repeated dose toxicity study shows no adverse effect of calcium chloride on rats fed on 1000–2000 mg/kg bw/day for 12 months. Calcium and chloride are both essential nutrients for humans and a daily intake of more than 1000 mg each of the ions is recommended. Genetic toxicity of calcium chloride was negative in the bacterial mutation tests and the mammalian chromosome aberration test. No reproductive toxicity study has been reported. A developmental toxicity study reveals no toxic effects on dams or fetuses at doses up to

189 mg/kg bw/day (mice), 176 mg/kg bw/day (rats) and 169 mg/kg bw/day (rabbits). (from: SIDS. Screening Information Data Set for High Production Volume Chemicals. (2005)).

Potassium chloride (KCl)

Potassium chloride is an essential constituent of the body for intracellular osmotic pressure and buffering, cell permeability, acid-base balance, muscle contraction and nerve function. Acute oral toxicity of KCl in mammals is low. In humans, acute oral toxicity is rare because large single doses induce nausea and vomiting, and because KCl is rapidly excreted in the absence of any pre-existing kidney damage. The toxicity upon repeated dose exposure is low. A threshold concentration for skin irritancy of 60 % was seen when KCl in aqueous solution was in contact with skin of human volunteers. The threshold concentration when applied to broken skin was 5%. No gene mutations were reported in bacterial tests, with and without metabolic activation. However, high concentrations of KCl showed positive results in a range of genotoxic screening assays using mammalian cells in culture. The action of KCl in culture seems to be an indirect effect associated with an increased osmotic pressure and concentration. No evidence of treatment -related carcinogenicity was observed in rats administered up to 1,820 mg KCl/kg body weight/day through the food in a two-year study. A developmental study revealed no foetotoxic or teratogenic effects of KCl in doses up to 235 mg/kg/day (mice) and 310 mg/kg/day (rats). Gastro- intestinal irritant effects in humans caused by KCl administrated orally have been reported at doses from about 31 mg/kg bw/day. One epidemiological investigation among potash miners disclosed no evidence of predisposition of underground miners to any of the diseases evaluated, including lung cancer. (from: SIDS. Screening Information Data Set for High Production Volume Chemicals. (2004)).

Sodium chloride (NaCl)

Sodium chloride is an essential nutrient for the normal functioning of the body. It is important for nerve conduction, muscle contraction, correct osmotic balance of extra cellular fluid and the absorption of other nutrients. Although rare, acute toxicity may be caused by ingestion of 500–1,000 mg sodium chloride/kg body weight. Symptoms include vomiting, ulceration of the gastrointestinal tract, muscle weakness and renal damage, leading to dehydration, metabolic acidosis and severe peripheral and central neural effects. Long-term effects of high (>6 g/day) dietary sodium chloride include the development of hypertension, and may increase the risk of kidney stone formation and left ventricular hypertrophy. In rodents, extremely high doses of sodium chloride during pregnancy caused musculoskeletal abnormalities, foetotoxicity and foetal death and post- implantation mortality and abortion. Sodium chloride has been demonstrated to be a gastric tumour promoter

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

in experimental animals and high sodium chloride intakes have been associated with incidence of stomach cancer in human populations with traditional diets of highly concentrated, salted foods. (Expert Group on Vitamins and Minerals (2003), www.food.gov.uk/science/ouradvisors/vitandmin/evmpapers)

Zinc bromide (ZnBr2)

Zinc bromide inhalation can cause severe irritation of mucous membranes and upper respiratory tract. Symptoms may include burning sensation, coughing, wheezing, laryngitis, shortness of breath, headache, nausea and vomiting. High concentrations may cause lung damage. Ingestion of zinc bromide can cause severe burns of the mouth, throat, and stomach. Can cause sore throat, vomiting and diarrhoea. Ingestions are usually promptly rejected by vomiting, but sufficient absorption may occur to produce central nervous system, eye and brain effects. Symptoms may include skin rash, blurred vision and other eye effects, drowsiness, irritability, dizziness, mania, hallucinations, and coma.

Causes severe skin irritation with redness, itching and pain. May cause burns, especially if skin is wet or moist. Can cause severe eye irritation or burns with eye damage.

Repeated or prolonged exposure by any route may cause skin rashes (bromaderma). Repeated ingestion of small amounts may cause central nervous system depression, including depression, ataxia, psychoses, memory loss, irritability and headache.

Calcium bromide (CaBr2)

Calcium bromide brine is a highly concentrated aqueous solution of calcium bromide and calcium chloride. It is used extensively in the oil industry. This solution and its components are recognized as causes of skin injury and information is available from the manufacturers on their safe use and handling. Two patients who were injured following unprotected skin exposure to this solution and one patient who was injured following exposure to calcium chloride powder are reported. All sustained skin injuries characterized by an absence of pain and a delayed clinical appearance of the full extent of the injury. Furthermore healing was complicated by graft loss or was slow. Although organic bromine compounds are recognized as a cause of skin injuries, no previous reports of such injuries to humans secondary to calcium chloride or bromide exposure were found in the medical literature. Our experience with these patients is described. (Saeed et al., Burns; 23 (7–8)32. 1997. 634–637)

Sodium bromide (NaBr)

Sodium bromide is of low acute oral toxicity. Sodium bromide is expected to be a slight to moderate eye irritant. Repeated or prolonged skin contact may cause irritation and superficial burns. Available data indicate that sodium bromide may act as a teratogen (behavioural effects).

Sodium formate (NaCOOH)

Sodium formate is of low acute oral toxicity (LD50 oral rat > 3000 mg/kg). Data show that sodium formate is slightly irritating to the eye. Based on read-across from caesium formate, sodium formate is expected to be slightly irritating to skin. Sodium formate is not expected to be a skin sensitizer. Sodium formate at 1% in drinking water did not produce clinically adverse effects in rats after administration for approximately

18 months. Sodium formate is not genotoxic in vitro or in vivo. Based on read-across with calcium formate, sodium formate is not expected to be reprotoxic or carcinogenic.

Potassium formate (KCOOH)

Potassium formate is of low acute oral toxicity (LD50 oral mouse 5500 mg/kg). Data show that potassium formate is slightly irritating to the eye. Based on read-across from caesium formate, potassium formate is expected to be slightly irritating to skin. Potassium formate is not expected to be a skin sensitizer. Repeated- dose toxicity tests are not available; however, the metabolite formic acid did not cause significant toxicity to rats when administered in their drinking water at 0.5 and 1% for 2 to 27 weeks. Based on read-across with calcium formate, potassium formate is not expected to be reprotoxic or carcinogenic.

Caesium formate (CsCOOH)

Caesium formate solution (83%) is harmful upon ingestion (LD50 = 1780 mg/kg in rats), with clinical signs including depression, convulsions, respiratory distress, ataxia, and excessive salivation. Caesium formate monohydrate had low dermal (LD50 >2000 mg/kg) toxicity in rats, with signs of erythema noted at sites of application. Caesium formate solution (83%) was a slight skin irritant and a moderate eye irritant. Aqueous caesium formate (80% w/v) was not sensitizing to guinea pigs in a Buehler test. Repeated-dose toxicity tests are not available; however, the metabolite formic acid did not cause significant toxicity to rats when administered in their drinking water at 0.5 and 1 % for 2 to 27 weeks. The caesium cation is not expected to produce significant chronic toxicity. Caesium formate was not mutagenic in different in vitro assays. (National Industrial Chemicals Notification and Assessment Scheme (NICNAS), Australia, 2001).

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Density (weighting agents)

Barite (Barium sulphate)

Studies in rats using a soluble salt (barium chloride) have indicated that the absorbed barium ions are distributed via the blood and deposited primarily in the skeleton. The principal route of elimination for barium following oral, inhalation, or intratracheal administration is in the faeces. Following introduction into the respiratory tract, the appearance of barium sulphate in the faeces represents mucociliary clearance from the lungs and subsequent ingestion. In humans, ingestion of high levels of soluble barium compounds may cause gastroenteritis (vomiting, diarrhoea, abdominal pain), hypopotassaemia, hypertension, cardiac arrhythmias, and skeletal muscle paralysis. Insoluble barium sulphate has been extensively used at large doses (450 g) as an oral radiocontrast medium, and no adverse systemic effects have been reported. No experimental data are available on barium sulphate; however, due to the limited absorption of barium sulphate from the gastrointestinal tract or skin, it is unlikely that any significant systemic effects would occur. The acute oral toxicity of barium compounds in experimental animals is slight to moderate. Barium nitrate caused mild skin irritation and severe eye irritation in rabbits. The lack of reports of skin or eye irritation in humans, despite its widespread use, suggests that barium sulphate, often used as a contrast medium, is not a strong irritant. Long-term studies of barium exposure in laboratory animals have not confirmed the blood pressure, cardiac, and skeletal muscle effects seen in humans and laboratory animals orally exposed to acutely high levels. Inhalation exposure of humans to insoluble forms of barium results in radiological findings of baritosis, without evidence of altered lung function and pathology. Animal studies involving respiratory tract instillation of barium sulphate have shown inflammatory responses and granuloma formation in the lungs; this would be expected with exposure to substantial amounts of any low-solubility dust, leading to a change in lung clearance and subsequently to lung effects. Currently available data indicate that barium does not appear to be a reproductive or developmental hazard. Barium was not carcinogenic in standard National Toxicology Program rodent bioassays. In vitro data indicate that barium compounds have no mutagenic potential. The critical end-points in humans for toxicity resulting from exposure to barium and barium compounds appear to be hypertension and renal function. The NOAEL in humans is 0.21 mg barium/kg body weight per day. (www.inchem.org/documents/cicads/cicads/cicad33.htm, Concise International Chemical Assessment Document 33, Barium and barium compounds.)

Calcium carbonate

Acute effects may include irritation of skin, eyes, and mucous membranes. Based on an oral LD50 in rats of 6,450 mg/kg, calcium carbonate is of low oral acute toxicity. There is no adequate evidence for a tumour- promoting or genotoxic action of calcium carbonate. Effects on reproduction have not been shown. High dietary levels inducing maternal toxicity resulted in decreased fetal weights and delayed skeletal and dental calcification in rats and/or mice. There may be a silicosis risk in using impure limestone or chalk containing (3–20%) quartz. No adverse health effects have been reported in the literature among workers using calcium carbonate. High oral doses did not produce systemic toxicity in laboratory animals.

(Health Council of The Netherlands, 2003, calcium carbonate.)

Iron carbonate

Most data from iron compounds are derived from read-across with the ferrous salt iron sulphate. Ferrous sulphate has a low to moderate acute toxicity with a LD50 (rat) of 319–1,480 mg/kg. As ferrous sulphate is used in humans for the treament of anaemia, human data are also available. These indicate that the human LD50 is in the range of 40–1,600 mg/kg. Fatal doses are associated with gastric injury. Irritation data are scarce and indicate that ferrous sulphate may be irritating to skin and eyes. Ferrous sulphate is not a sensitizer. Genotoxicity data on ferrous sulphate are ambiguous. However. the overall weight of evidence from genotoxicity studies shows that ferrous sulphate is not genotoxic. Carcinogenicity is not expected. Ferrous sulphate is not a reprotoxicant. A study in calves fed up to 4000 ppm ferrous carbonate in diet shows that the calves were not affected. The tolerance for ferrous carbonate was higher than for ferrous sulphate.

Hematite

There are little data on hematite (or Fe2O3) available. The acute oral toxicity LD50 (rat) for Fe2O3 is greater than 10 g/kg. Upon eye contact some mechanical eye irritation may occur (dust). A carcinogenicity study in miners shows that haematite mining with low-grade exposure to radon daughters and silica dust was not associated with excess lung cancer in a relatively large cohort.

Ilmenite

There are no toxicity data available for ilmenite, or iron titanium oxide. It is expected that ilmenite is of low toxicity. There are no known hazards resulting from accidental ingestion of ilmenite sand as may occur during normal handling. Swallowing a large amount may result in irritation to the digestive system due to abrasiveness. Ilmenite dust may cause mechanical irritation of the eye. Ilmenite dust is regarded as general nuisance dust, but can be irritating if inhaled at high concentration. May cause symptoms such as coughing or sneezing.

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Manganese tetroxide

Manganese tetraoxide is of low acute toxicity. Mn3O4 is not a skin irritant, nor a sensitizer. Mn3O4 dust may cause some mechanical irritation to the eye. Results from a repeated dose study in monkeys and rats exposed to 11.6, 112.5 and 1,152 μ Mn3 as Mn3O4 aerosol 24 h/day for 9 months, show no exposure related effects on pulmonary function, limb tremor or electromyographic activity.

There are several reports about manganese toxicity as a result of exposure to fume/vapour from elemental manganese and by inhalation of pyrolusite (MnO2). Long-term inhalation (years) of manganese oxides may cause chronic manganese intoxication affecting the central nervous system, potentially leading to extensive disablement. Health risk of MnO2 (widely described in literature) may be different from that of MnO, Mn2O3, and Mn3O4. The differences in oxidation states of the element Mn in these compounds may affect their bioavailability and distribution and thus their potential effects.

Viscosity

Bentonite (or other clays)

An important determinant of the toxicity of bentonite and other clays is the content of quartz (SiO2). Exposure to quartz is causally related to silicosis and lung cancer. Statistically significant increases in the incidence of or mortality from chronic bronchitis and pulmonary emphysema have been reported after exposure to quartz.

Single intratracheal injection into rodents of bentonite and montmorillonite with low content of quartz produced dose- and particle size-dependent cytotoxic effects, as well as transient local inflammation, the signs of which included oedema and, consequently, increased lung weight. Single intratracheal exposures of rats to bentonite produced storage foci in the lungs 3–12 months later. After intratracheal exposure of rats to bentonite with a high quartz content, fibrosis was also observed. Bentonite increased the susceptibility of mice to pulmonary infection. No adequate studies are available on the carcinogenicity of bentonite. Long-term occupational exposures to bentonite dust may cause structural and functional damage to the lungs. However, available data are inadequate to conclusively establish a dose-response relationship or even a cause-and-effect relationship due to limited information on period and intensity of exposure and to confounding factors, such as exposure to silica and tobacco smoke. (Environmental Health Criteria, Vol. 231 (2005) 159 p.)

Organophillic clay (montmorillonite, attapulgite, hectorite)

In general, the acute toxicity of organophillic clays is low. Some organophillic clays are used in cosmetics. Data on a hectorite clay show that the clay is of low acute and repeated dose toxicity. The clay is not a skin or eye irritant, nor a skin sensitizer. In dust form the hectorite clay may cause mechnical eye irritation. Data indicate that the hectorite clay is not genotoxic. Data on reprotoxicity and carcinogenicity are not available.

Check the MSDS for the compound-specific information.

Biopolymers

The biopolymers used are generally low toxicity compounds. Some of these biopolymers are also used as food additive. Check the MSDS for the compound-specific information.

Carboxymethyl cellulose

Carboxymethyl cellulose is of low toxicity. Carboxymethyl cellulose is approved for and used as food additive. (WHO Food Additives Series, Vol. 42 (1999) pp 175–9)

Polyanionic cellulose

Cellulose compounds are generally low toxicity compounds. Some of these cellulose compounds are also used as food additive. Check the MSDS for the compound-specific information. (WHO Food Additives Series, Vol. 40 (1998) pp 55–78; and WHO Food Additives Series Vol. 42 (1999) pp 175–9)

Guar gum (polysaccharide)

Guar gum is a low toxicity compound, commonly used as food additive. Allergic rhinitis following repeated inhalation exposure to guar gum dust has been reported. (Lagier et al., 1990, J. Allergy Clin Immun, 85(4)
p. 785–790; Kanerva et al., 1988, Clin Allergy, 18(3) p245–252)

Emulsifiers

Soaps

See Table 2. Several emulsifiers may irritate skin and/or eye and may be harmful by inhalation or if swallowed. Check the MSDS for the compound-specific information.

Amines

See Table 2. Several emulsifiers may irritate skin and/or eye and may be harmful by inhalation or if swallowed. Check the MSDS for the compound-specific information.

Imidazolines

See Table 2. Several emulsifiers may irritate skin and/or eye and may be harmful by inhalation or if swallowed. Check the MSDS for the compound-specific information.

Polyamides

See Table 2. Several emulsifiers may irritate skin and/or eye and may be harmful by inhalation or if swallowed. Check the MSDS for the compound-specific information.

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Dispersants

Modified polyacrylates

Modified polyacrylates is a general term for several specific polyacrylates each having compound-specific toxicological properties. Check the MSDS for the compound-specific information.

Lignosulphonates

Lignosulphonates are complex polymers with a broad range of molecular mass and are derived from trees. The wood from trees is composed mainly of three components—cellulose, hemicellolose and lignin. In the sulphite pulping process, the lignins are sulphonated so they become water soluble and thus can be separated from the insoluble cellulose. A review of available toxicity data on several lignosulphonates by the US EPA indicated that lignosulphonates are of very low toxicity (www.epa.gov [Federal Register: February 16, 2005 (Volume 70, Number 31)]). The oral acute LD50 values are all greater than 2 g/kg. Repeated dose studies indicate NOAELs and LOAELs in the order of magnitude of g/kg/day. There is some (unsubstantiated) information that lignosulphonates given to rats before, during, and after mating at doses as high as 1,500 mg/kg/day did not cause adverse effects on reproduction or offspring. But at a dose level of 500 mg/kg/day there were histopathological changes in the lymph nodes of the mothers. There were no concerns identified for the mutagenicity or carcinogenicity of lignosulphonates. Based on the physical/chemical properties, and particularly on the large molecular weights of the lignosulphonates, lignosulphonates are not likely to be absorbed via any route of exposure. The only health effects of concern upon exposure to lignosulphonates are irritation of skin, eyes and respiratory system. For some lignosulphonates contact allergy has been reported (Andersson et al., 1980; Contact Dermatitis 6(5): 354–355). The toxicity depends on the type and size of the lignosulphonate. Check the MSDS for the compound-specific information.

Tannins

Tannins are polyphenols derived from plants. Due to their ubiquitous presence in food they have been subject of many toxicity studies. In general, tannins are of low acute toxicity. Tannins in food have been associated with several beneficial and adverse health effects (Chung et al., 1998 Crit Rev Food Sci Nutr 38(6): 421–64). IARC has evaluated tannic acid and tannins and concluded that although tannins were carcinogenic in animals upon subcutaneous injection, no epidemiological evidence in humans was available to evaluate their toxicity in humans. (IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Some Naturally Occurring Substances, Vol. 10, pages 253–262). Check the MSDS for the compound-specific information.

Fluid loss

Synthetic polymers

Check the MSDS for the compound-specific information.

Carboxymethyl celullose

See above (viscosity)

Polyanionic cellulose

See above (viscosity)

Starch

Starch is a low toxicity compound, commonly used as food additive.

Bentonite

See above (viscosity)

Modified lignites

Modified lignites are derived from brown coal. The toxicity mainly depends on the modification. Check the MSDS for the compound-specific information.

Asphalt

Asphalt, more commonly referred to as bitumen in Europe, is a dark brown to black, cement-like semisolid or solid or viscous liquid produced by the non-destructive distillation of crude oil during petroleum refining. When asphalts are heated, vapours are released; as these vapours cool, they condense. As such, these vapours are enriched in the more volatile components present in the asphalt and would be expected to be chemically and potentially toxicologically distinct from the parent material. Asphalt itself is considered to be of low toxicity. Asphalt fumes are the cloud of small particles created by condensation from the gaseous state after volatilization of asphalt. Symptoms associated with asphalt fume exposure are eye, nose, and throat irritation and coughing. These health effects appear to be mild in severity and transient in nature. Additional symptoms include skin irritation, pruritus, rashes, nausea, stomach pain, decreased appetite, headaches, and fatigue, as reported by workers involved in paving operations, insulation of cables, and the manufacture of fluorescent light fixtures. Asphalt fumes and vapours may be absorbed following inhalation and dermal exposure. Results of several in vitro mutagenicity studies on asphalt fumes are ambiguous. Results of carcinogenicity studies indicate that some asphalt fume condensates can cause tumours when applied dermally to mice. A meta- analysis of 20 epidemiological studies failed to find overall evidence for a lung cancer risk among pavers and highway maintenance workers exposed to asphalt. Under various performance specifications, it is likely that asphalt fumes contain carcinogenic substances.
(Concise International Chemical Assessment Document (CICAD) Vol. 59 (2004))

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Resins

There are several types of resins, both naturally derived and synthetic. The toxicological properties vary. Some resins have been associated with skin irritation and allergic contact dermatitis. Check the MSDS for the compound-specific information.

Gilsonite

Gilsonite is a form of natural asphalt found in large amounts in the Uintah Basin of Utah. Workers can be exposed to the dust of gilsonite and to the fumes of gilsonite when heating or boiling the material. Gilsonite dust may cause mechanical eye irritation, while the fumes may be irritating to the eyes and respiratory system (Fairhall (1950) Industrial Hygiene Newsletter, 10(5): 9-10).

Industrial hygiene characterizations were performed by NIOSH at three gilsonite mills and nine gilsonite mining operations to measure occupational exposure to gilsonite and its constituents and to evaluate potential health effects (Kullman et al., Am Ind Hyg Assoc J (1989) 50(8): 413–418). Six out of seven bulk gilsonite samples had crystalline silica contents below 0.75% wt., no asbestos or other fibrous mineral compounds were detected in bulk samples from five different veins of gilsonite, and polynuclear aromatic hydrocarbons were not detected in any bulk samples. The authors conclude that the gilsonite dust exposure data are consistent with results of an earlier respiratory health survey of gilsonite workers in which the most definitive finding was an excess prevalence of bronchitic symptoms.

The respiratory health survey (Keimig et al., Am J Ind Med. (1987); 11(3): 287–296) showed that increased prevalences of cough and phlegm were found in workers with high-exposure jobs, but no evidence for dust- related pulmonary function impairment was noted.

Inhibition

Salts

See above (osmotic—salts)

Glycols (polyglycols)

Glycols, glycol ethers and polyglycols have different toxicities. Polyglycols are generally of low toxicity. Check the MSDS for the compound-specific information.

Silicate

The most commonly used silicates in drilling fluids are potassium silicate and sodium silicate. These ingredients combine metal cations (potassium or sodium) with silica to form inorganic salts. Sodium silicate administered orally acts as a mild alkali and is readily absorbed from the alimentary canal and excreted in the urine. The toxicity of silicates has been related to the molar ratio of Si02/Na20 and the concentration. Potassium and sodium silicates have a low to moderate acute toxicity. Rats orally administered 464 mg/kg of a 20% solution containing either 2.0 or 2.4 ratio to 1.0 ratio of sodium oxide showed no signs of toxicity, whereas doses of 1,000 and 2,150 mg/kg produced gasping, dypsnea, and acute depression. A case report describes that neutralized sodium silicate produced vomiting, diarrhea, and gastrointestinal bleeding in human.

Dermal irritation of potassium silicate and sodium silicate ranged from negligible to severe, depending on the species tested and the molar ratio and concentration tested. Potassium silicate was non-irritating in two acute eye irritation studies in rabbits. Sodium silicate was a severe eye irritant in acute eye irritation studies. A skin freshener (10% of a 40% aqueous solution) containing sodium silicate was non-irritating. Sodium silicate in another three eye irritation studies was highly irritating, irritating, and nonirritating, respectively. Detergents containing 7%,13%, and 6% sodium silicate mixed 50/50 with water were negligible skin irritants to intact and abraded human skin. A 10% of a 40% aqueous solution of sodium silicate was negative in a repeat-insult predictive patch test in humans. The same aqueous solution of sodium silicate was considered mild under normal use conditions in a study of cumulative irritant properties. Sodium silicate tested in elbow crease studies and semioccluded patch tests, produced low grade and transient irritation.

Repeated dose studies in Beagles and rats showed no overt signs of toxicity.

Sodium silicate was non-mutagenic in a standard bacterial assay. Reprotoxicity studies with sodium silicate in rats showed some effects on the number of offspring at high doses but no effects on male rat fertility.
(Int J Toxicol Vol. 24 Suppl. 1 (2005) pp 103–7)

Polyacrylamides (partially hydrolysed)

There are various different types of polyacrylamides. Check the MSDS for the compound-specific information.

pH control

Sodium hydroxide (NaOH)

Sodium hydroxide is a skin and eye corrosive. In a human 4-hour patch test, sodium hydroxide (0.5%) was a very clear skin irritant. Irritation of the nose, throat, or eyes was observed in workers engaged in cleaning operations and in a small number of users of an oven spray. Ingestion might be fatal, as a result of, e.g., shock, infection of the corroded tissues, pulmonary necrosis, or asphyxia. No increase in mortality in relation to duration or intensity of exposure to caustic dust was found in a group of 265 workers for periods ranging from less than

1 year to up to 30 years. (Health Council of The Netherlands, 2000, sodium hydroxide)

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Potassium hydroxide (KOH)

Potassium hydroxide is a skin and eye corrosive. Following ingestion of (a solution of ) potassium hydroxide, rapid corrosion and perforation of the oesophagus and stomach, stricture of the oesophagus, violent pain in throat and epigastrium, haematemesis, and collapse may occur. When inhaled in any form, potassium hydroxide is strongly irritating to the upper respiratory tract. Acute exposures may cause symptoms in the respiratory tract including severe coughing and pain. Additionally, lesions may develop along with burning of the mucous membranes. Inhalation may be fatal as a result of spasm, inflammation, and oedema of the larynx and bronchi, chemical pneumonitis, and pulmonary oedema (which can develop with a latency period of 5–72 hours). Chronic exposures may cause inflammatory and ulcerative changes in the mouth and possibly bronchial and gastrointestinal disorders. It has been reported that 10% of workers exposed to KOH during the production of ascorbic acid developed allergic dermatitis. At least one case of oesophageal carcinoma at the site of hydroxide- induced strictures has been reported. In mice, repeated applications of aqueous solutions (3-6%) of KOH to the skin for 46 weeks resulted in an increased incidence of skin tumours. Since tumourigenesis was associated with severe skin damage inducing marked epidermal hyperplasia, a non-genotoxic mechanism is assumed.

(Health Council of The Netherlands, 2004, potassium hydroxide)

Calcium hydroxide (Ca(OH)2) Lime

Acute exposures to calcium hydroxide may cause irritation, along with coughing, pain, and possibly burns of the mucous membranes with, in severe acute exposures, pulmonary oedema and hypotension with weak and rapid pulse. Solid calcium hydroxide is corrosive to the eyes and may cause severe injury to the skin. There are numerous case reports on accidental exposures to calcium hydroxide resulting in corneal and skin alkali burns and caustic ulcers. Generally, these effects are caused by the solid material and less commonly or rarely by solutions. Ingestion of alkali is reported to be followed by severe pain, vomiting (containing blood and desquamated mucosal lining), diarrhoea, and collapse.

Two epidemiological studies that addressed the association between cement-dust exposure and stomach cancer were considered insufficient to reach any conclusions on the association between cement dust exposure and stomach cancer. However, no adverse effects have been experienced by long-term exposed workers. Oral LD50 values of approximately 7,300 mg/kg bw were reported for rats and mice. No adequate repeated-dose toxicity (including carcinogenicity and reproduction toxicity) or genotoxicity/mutagenicity studies are available. (Health Council of The Netherlands, 2004, calcium hydroxide)

Citric acid

Based on many experimen tal data in animals and on human experience, citric acid is of low acute toxicity. The NOAEL for repeated dose toxicity for rats is 1200 mg/kg/d. The major, reversible (sub)chronic toxic effects seem to be limited to changes in blood chemistry and metal absorption/excretion kinetics. Citric acid is not suspected of being a carcinogen nor a reprotoxic or teratogenic agent. The NOAEL for reproductive toxicity for rats is 2500 mg/kg/d. Further, it is not mutagenic in vitro and in vivo. Also, the sensitizing potential is seen as low. In contrast, irritation, in particular of the eyes but also of the respiratory pathways and the skin, is the major toxicological hazard presented by citric acid.

(SIDS. Screening Information Data Set for High Production Volume Chemicals, 2004)

Sodium bicarbonate (NaHCO3)

Sodium bicarbonate is of low acute toxicity. Oral LD50 values are higher than 4,000 mg/kg bw, and an inhalation study in rats using a concentration of 4.74 mg/l inhalable dust produced no deaths. Sodium bicarbonate is slightly irritating to the skin and eye of rabbits. There is no indication of any adverse effects of long-term use or exposure via any route. In vitro bacterial and mammalian cell tests showed no evidence of genotoxic activity. Sodium bicarbonate is not a reprotoxicant. Based on the available information there are no indications that sodium bicarbonate has carcinogenic effects. Sodium bicarbonate has a long history of use in food and normal handling and use will not have any adverse effects. Acute oral ingestion of high doses may result in a ruptured stomach due to excessive gas development. Acute or chronic excessive oral ingestion may cause metabolic alkalosis, cyanosis and hypernatraemia. These conditions are usually reversible, and will not causeadverseeffects. (SIDS.ScreeningInformationDataSetforHighProductionVolumeChemicals,2003)

Calcium oxide (CaO; Quick lime)

Occupational and accidental exposures have shown calcium oxide to be very irritating and corrosive to mucous membranes, eyes, and moist skin because of local liberation of heat and dehydration of tissues upon slaking of the small size particles and the resulting alkalinity of the slaked product (calcium hydroxide). Fatal burns have been reported after massive exposure. Calcium oxide was stated not to be sensitizing in an open epicutaneous test. Calcium oxide can cause severe irritation and burns to the eyes, oedema, hyperaemia, lachrymation, blurred vision, corneal opacities, ulceration, and perforation and loss of vision. Inflammation of the respiratory passages, ulceration, perforation of the nasal septum, and pneumonia have been attributed to inhalation of calcium oxide dust. Workers in lime factories for up to 40 years have experienced no ill effects from exposure to lime. (Health Council of The Netherlands, 2006, calcium oxide)

Table 1: Health hazards of drilling fluid components (continued)

Component

Human health hazard

Wetting agent

Sulphonic acid

Sulphonic acids are a class of organic acids which have the tendency to bind to proteins and carbohydrates. The salts of sulphonic acids are the sulphonates. The toxicity of sulphonic acids depends on the specific type. Sulphonic acids may be irritating to skin and/or eye. Check the MSDS for the compound-specific information.

Amides

Amides are formed from the reaction of a carboxylic acid with an amine and are, compared to amines, very weak bases. The toxicity of amides depends on the specific type. Amides may be irritating to skin and/or eye. Check the MSDS for the compound-specific information.

Polyamides

There are different types of polyamides with a different toxicity. Check the MSDS for the compound-specific information.

Rheological modifier

Fatty acids

Fatty acids are aliphatic monocarboxylic acids and can be naturally derived (from animal or vegetable fat) or synthetic (from oil or wax). Fatty acids are generally low toxicity compounds. Check the MSDS for the compound-specific information.

Polyacrylates

See above (dispersants)

Filtration control

Asphalt

See above (fluid loss)

Lignite

See above (fluid loss)

Gilsonite

See above (fluid loss)

Lubricating agents

Ester oils

Check the MSDS for the compound-specific information.

Asphalts

See above (fluid loss)

Graphite

In humans, the pathological and physiological response to inhaled graphite flake is similar to that induced by nuisance dusts and cause only transient pulmonary changes. Repeated exposure to very high concentrations may overwhelm the clearance mechanisms of the lung and result in pulmonary damage from the retained particles in unprotected individuals. However, these lesions either resolve with time or are of limited severity. Driver et al. (1993), Govt Reports Announcements & Index (GRA&I), Issue 06, 2094.

Other

Bactericides

Check the MSDS for the compound-specific information.

Lost Circulation Material (CaCO3, graphite, walnut shells, mica)

Lost circulation material may form a generic dust hazard. Mechanical irritation to the eyes and respiratory system may occur.

Ammonium bisulphate (max 63% aq. solution)

Ammonium bisulphate in solution is irritant to eyes and skin, and is irritating to the respiratory system. Inhalation of dust can produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing.

Sodium sulphite (approx 50% aq. solution)

Sulphites that enter mammals via ingestion, inhalation, or injection are metabolized by sulphite oxidase to sulphate. Sodium sulphite is of low to moderate acute toxicity. The oral mouse LD50 is 820 mg/kg. Exposure to the aerosol may irritate the upper respiratory tract. A three-day exposure of rats to a sodium sulphite aerosol produced mild pulmonary edema following exposure to 5 mg/m3, and irritation of the tracheal epithelium with 15 mg/m3. Between 2% and 5% of asthmatics are sulphite sensitive. Sodium sulphite may be irritating to skin and eyes. Positive reaction in human patch tests have been reported. Sodium sulphite is not considered to be reprotoxic; in rats, sodium sulphite heptahydrate at large doses (up to 3.3 g/kg) produced fetal toxicity but not teratogenicity. Sodium sulphite was negative in genotoxicity studies. IARC concluded that sodium sulphite is not classifiable (group 3) as to their carcinogenicity for humans. (Int J Toxicol Vol. 22, Suppl. 2 (2003) p. 63–88)