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Priority Existing Chemical Assessment Reports

PEC No. 5

Sodium Ethyl Xanthate

Introduction

Sodium ethyl xanthate (CAS No 140-90-9) was declared a priority existing chemical by the Minister of Industrial Relations by notice in the Chemical Gazette of 6 July 1993.

Importers of sodium ethyl xanthate were obliged under section 55 of the Commonwealth Government's Industrial Chemicals (Notification and Assessment) Act 1989 to apply for its assessment. Sodium ethyl xanthate is not manufactured in Australia.

Information for assessment was obtained from the applicants, end-users and scientific literature.

Applicants

ICI Australia Pty Ltd
1 Nicholson Street
Melbourne VIC 3000

Quantum Chemicals Pty Ltd

Suite 4

21 Kitchener Parade

Bankstown NSW 2200

Mineral and Chemical Traders Pty Ltd

59 Parraween Street

Cremorne NSW 2090

Redox Chemicals Pty Ltd

30&endash;32 Redfern Street

Wetherill Park NSW 2164

Mintrade Pty Ltd

Level 1

14 Edmonstone Street,

South Brisbane QLD 4101

Renison Limited

Renison Tin Division

P O Box 20

Zeehan TAS 7469

Chemical identity

Sodium ethyl xanthate is listed in the Australian Inventory of Chemical Substances as carbonodithioic acid, O-ethyl ester, sodium salt, and has a molecular weight of 141.14.

The chemical Abstract Services Number for sodium ethyl xanthate is 140-90-9.

Use

Sodium ethyl xanthate is used in the mining industry as a flotation agent in the separation of metal sulphides. It is mainly used for the separation of copper, nickel, lead, gold and zinc. During use, the solid sodium ethyl xanthate is mixed with water to form a dilute aqueous solution, and concentrations in the order of 10% are used. The pH of the aqueous solutions range typically from 7 to 11. Sodium ethyl xanthate is not manufactured in Australia and approximately 2,500 tonnes - in powder and pellet form - is imported per annum.

Physical and chemical properties

Sodium ethyl xanthate is a pale yellow amorphous powder with a disagreeable odour due to the presence of carbon disulphide. It has a melting point of 182&endash; 256┬░C, specific gravity 1.263, water solubility 450 g/L at 10┬░C and is non-volatile at 25┬░C. The chemical hydrolyses very rapidly under acidic conditions and is stabilised by high pH conditions. It dissociates totally under pH 9. Sodium ethyl xanthate is hygroscopic and reacts with water to form carbon disulphide, ethyl alcohol, sodium carbonate and trithiocarbonate.

Carbon disulphide is the major decomposition product and has a low autoignition point (99┬░C) and is highly flammable. The physico-chemical properties of carbon disulphide are: odour threshold 0.02 ppm (perception in humans); boiling point 46.5oC; specific gravity 2.1 g/L; vapour pressure 40 kPa; flash point -30oC (closed cup); and is explosive at 1.3&endash;50% v/v in air. It reacts strongly with oxidising agents.

Decomposition of xanthates

Sodium ethyl xanthate is stable if stored under dry, cool conditions. However, exposure of solid xanthates to moisture and heat causes decomposition and formation of carbon disulphide. The heat generated by hydration or decomposition could raise the temperature to the auto-ignition point of carbon disulphide.

Xanthates decompose in aqueous solution by dissociation, oxidation and hydrolysis. Hydrolytic decomposition is the main reaction in alkaline solutions while the other two reactions occur in acidic solutions. Sodium ethyl xanthate is used in the flotation process in alkaline conditions, and therefore the main reaction is hydrolytic decomposition and the major decomposition product is carbon disulphide.

Decomposition of xanthates is accelerated at high concentrations and raised temperatures and is also rapid at pH below 7 and decreases as the pH increases.

Hazard assessment Animal toxicological data

Assessment of sodium ethyl xanthate revealed a lack of published and unpublished toxicity data. The limited and generally poor quality toxicity data creates difficulties in predicting potential human health effects. Toxicity data for other xanthates was included in the assessment for completeness.

Sodium ethyl xanthate as a 10% solution at a pH of 10.5-11 has an oral LD50 of 730 mg/kg in mice. The target sites are the central nervous system, liver and the spleen. Oral LD50 for other xanthates in mice range from 411&endash;583 mg/kg and in rats from 1000-2000 mg/kg.

The target sites for the adverse effects of potassium butyl xanthate both after single and repeated oral administration were the central nervous system, liver and kidneys indicating similar target organs for the various xanthates.

Sodium ethyl xanthate powder has a dermal LD50 <1000 mg/kg in rabbits and is a moderate skin irritant. A 10% solution is not a skin irritant.

Sodium ethyl xanthate as a powder causes mild to moderate eye irritation in the rabbit, while it is not an irritant in the diluted form (10% solution).

Inhalation of potassium amyl xanthate in a 30-day study produced adverse effects on the liver in dogs, rats and mice. The other affected organs were the kidneys in rats and the central nervous system in mice.

The target sites for sodium ethyl xanthate, and other xanthates are the central nervous system, liver and kidneys. The adverse effects seen in the toxicity studies could be due to the xanthates themselves, their decomposition products or a combination of both.

Human health effects

Limited human health effects information was available for assessment. Contract workers at one mining site reported nausea and residents in the vicinity of a mine using sodium ethyl xanthate complained of headache, dizziness, nausea and foul odour. A chemical leak during transport of sodium ethyl xanthate led to six railway workers being hospitalised after inhaling fumes.

The Canadian Centre for Occupational Health and Safety (1994) has summarised a report by Rakhimova (1973) of acute exposure of a worker who opened a tank containing sodium ethyl xanthate. The worker lost consciousness and was removed from the work site. On revival he was restless, vomited and had convulsive twitching of muscles in his arms and legs. He complained of difficult breathing, teary eyes and hoarseness and later developed light sensitivity and fluid accumulation in the eyelids and eye discharge.

Classification

In accordance with the health effects criteria detailed in the National Commission's Approved Criteria for Classifying Hazardous Substances (Approved Criteria), sodium ethyl xanthate is classified as 'harmful' by the oral and dermal routes and as an eye and skin irritant. The 10% solution of sodium ethyl xanthate is classified as harmful by the oral route and is not a skin and eye irritant. Based on the classification of its health effects and in accordance with the Approved Criteria sodium ethyl xanthate is considered to be a hazardous substance.

The data were insufficient to classify sodium ethyl xanthate for other health hazards such as chronic effects, acute inhalational effects, carcinogenicity and mutagenicity.

According to the Australian Code for the Transport of Dangerous Goods by Road and Rail (ADG Code) sodium ethyl xanthate is classified as a dangerous good, Class 4.3, that is, substances which in contact with water emit flammable gases.

Carbon disulphide

Carbon disulphide is a dangerous fire and explosion hazard.

Carbon disulphide can be absorbed by inhalation, through the skin and by the oral route. Acute exposure to high concentrations (500 to 1000 ppm) may result in psychosis and narcosis. Carbon disulphide vapour is a severe irritant to the eyes, skin and respiratory system, and the liquid may cause burns.

Repeated exposure to carbon disulphide vapour can adversely affect the central and peripheral nervous systems, including weakening of the leg muscles and damage to the peripheral and cerebral arteries. Carbon disulphide has been shown to contribute towards coronary heart disease in exposed workers, and severe effects on the retina of the eye have been observed. Hearing defects in workers exposed to carbon disulphide have also been reported.

Adverse effects on the reproductive system of workers has been noted. Menstrual disorders have been observed in female workers exposed to carbon disulphide levels below 3 ppm for 3 years. Decreased libido was observed in earlier studies while a later study revealed changes in sperm morphology when carbon disulphide levels were believed to be about 13&endash;26 ppm but with excursions up to 250 ppm.

Data from animal studies are consistent with the observed human health effects.

Exposure assessment Occupational exposure

Sodium ethyl xanthate is not manufactured in Australia and hence occupational exposure to sodium ethyl xanthate is limited to workers involved in the transport, use and storage of the chemical. A number of mines in Australia use sodium ethyl xanthate or one of the other alkyl xanthates.

Transport and storage

Sodium ethyl xanthate in pellet or powder form is usually imported in 110&endash;120 kg steel drums with an inner polyethylene liner or recently in plastic bulker bags containing 500&endash;700 kg. The quality of the packaging of the chemical varies from batch to batch.

Conditions of storage vary at different mine sites from a fully enclosed area to a large storage shed with only three walls. At some sites storage is in a covered area with only a roof and no walls.

One or two workers are involved in the handling and storage of drums at each mining site. There is the greatest potential for worker exposure to xanthate powder or pellets and carbon disulphide vapour during transport and storage if the drums or bulker bags are damaged or not adequately sealed. Sodium ethyl xanthate in contact with moisture produces carbon disulphide.

Mixing process

There is a potential for high worker exposure to sodium ethyl xanthate and carbon disulphide, during the mixing process, depending on the degree of automation. During tipping of the drums there is a likelihood of dust generation and spillage of the powder or pellets which could lead to worker exposure.

Storage of solution

Potential for exposure during storage of the solution is limited as transfer to the storage and header tanks are through closed pipes. Inhalation exposure could occur due to leaks in the pipes.

Flotation

Sodium ethyl xanthate solution enters the flotation cells through closed pipes via a head tank. The solution is gravity fed via control valves and flow meters to addition points within flotation cells. Workers involved in checking flows, the head tank or in adjusting and monitoring the pulp levels in the flotation process could be exposed to the chemical or carbon disulphide.

Maintenance

Storage tanks must be cleaned regularly due to the build up of sludge. The frequency of cleaning storage tanks varies from once every three months to once or twice a year at different mines. There is a high potential for dermal and inhalational exposure to both sodium ethyl xanthate and carbon disulphide during the cleaning of storage tanks. However, workers generally follow standard operating procedures for working in a confined space including use of personal protective equipment.

Dermal exposure to sodium ethyl xanthate solution and inhalation exposure to carbon disulphide could occur during repair or replacement of the plumbing system. Around 20 personnel are involved in general maintenance work for approximately 1 hour/week.

Sampling procedure

Dermal and inhalation exposure may occur to personnel involved in the collection of samples or analysis of sodium ethyl xanthate.

Incident reports

Two transport incidents have been reported in Alice Springs. One in May 1993 involved a chemical leak at the railway station. Six workers were hospitalised after inhalation of toxic fumes and 100 people were evacuated. The cargo consisted of 56 drums of sodium ethyl xanthate. Some of the drums had lost their lids and the inner plastic lining had ripped due to the inferior quality of the packaging and mechanical damage.

In another incident in 1984 approximately 20 steel drums of sodium ethyl xanthate had been loaded into a freight container together with medical equipment and supplies. On arrival of the container at its destination in Alice Springs it was found that a considerable quantity of the sodium ethyl xanthate dust had escaped from the drums and had permeated the medical equipment and supplies.

Fire incidents involving sodium ethyl xanthate have also been reported. In January 1994 a trial shipment of sodium ethyl xanthate packaged in 700 kg plastic bulker bags caught fire in the storage area at a mining site. The fire spread rapidly and three operations personnel and one fireman were affected by fume inhalation and hospitalised overnight. Most of the bulk sodium ethyl xanthate was severely affected by fire.

The fire was observed to spread quickly from bag to bag, whereas only one drum containing sodium ethyl xanthate in the area caught fire. This highlights a major problem with the use of bulker bags in contrast to drums. The material continued to reignite and was disposed of immediately. The company concluded that the most likely cause was ineffective sealing of the inner bag due to manual tying of the inner plastic bag leading to the escape of carbon disulphide and the likely cause of ignition was a spark associated with a forklift unloading steel drums at the time of the fire. However, spontaneous combustion cannot be ruled out.

In November 1994, a shipment of 80 bulker bags each containing 700 kg of potassium amyl xanthate was unloaded for testing at Fremantle the first port of call, following the issue of a product alert by the manufacturer. The containers were taken by road to a transport yard at O'Connor after two days at the Fremantle port to facilitate product testing (temperature measurement). Two of the bulker bags that were found to be "smoking" and another that was found to be unstable were placed in an empty freight container and isolated. The potassium amyl xanthate was allowed to burn under controlled conditions. The cause of the fire has not been determined. The likely cause may be spontaneous combustion following release of carbon disulphide.

In another incident, residents living in the vicinity of a mine using sodium ethyl xanthate complained of headache, dizziness, nausea and foul odour. Other symptoms reported were eye irritation, sore throat and impaired breathing. The ill effects were reported up to three kilometres from the mine site. The situation was thought to have been aggravated by the weather conditions. Atmospheric monitoring for carbon disulphide showed that the levels were below 10 ppm.

Atmospheric monitoring

Atmospheric monitoring for sodium ethyl xanthate is not carried out at the mine sites where it is used and there is no recognised methodology for sodium ethyl xanthate. Random instantaneous monitoring for carbon disulphide is carried out at some of these mine sites. However, very limited monitoring data was provided for this assessment.

The exposure standard for carbon disulphide recommended by the National Commission is a time weighted average (TWA) of 10 ppm. From the limited data submitted for assessment it appears that carbon disulphide levels at the mine sites are below the TWA. However, instantaneous samples using detector tubes indicate that at times, short-term excursions above 10 ppm occur in the mixing area during mixing activity at some sites. High levels were also recorded in the containers in ship holds on the arrival of sodium ethyl xanthate at the ports. The monitoring data indicate that there is the potential for exposure to high levels of carbon disulphide during mixing and transport. However, the data were inadequate to demonstrate how widespread this problem is and whether there is the potential for exposure in other areas or activities.

Public exposure

The public is unlikely to be exposed to sodium ethyl xanthate through its use as a flotation agent in the mining industry.

Since the compound decomposes and the major product is carbon disulphide, there exists some potential for the contamination of the immediate atmosphere which may impact on public health. This risk is minimised by the use of adequate transport and engineering controls, such as during transport incidents. Release of the hazardous degradation products may also result from the decomposition of residual amounts of sodium ethyl xanthate which remain in the aqueous phase in the tailings slurry, which is discharged to a tailings dam. However, such dams are typically located on remote sites and the residual concentrations of sodium ethyl xanthate are expected to be low.

Risk assessment Occupational health

Health effects data indicate that dermal exposure to sodium ethyl xanthate should be avoided, the generation of dust minimised and situations leading to the formation of carbon disulphide avoided.

Situations which are likely to present the greatest risk to workers are:

*

direct skin contact with sodium ethyl xanthate powder or pellets;
*

inhalational exposure to sodium ethyl xanthate dust;
*

direct skin contact with carbon disulphide;
*

inhalational exposure to carbon disulphide vapour; and
*

conditions which are conducive to carbon disulphide flammability.

High levels of worker exposure to both sodium ethyl xanthate and carbon disulphide may occur during the mixing process, clean up of spills, maintenance of equipment and cleaning of tanks. Adequate engineering controls, safe work practices and use of personal protective equipment would reduce risk to low levels.

Potential for fire is high during transport and storage if packaging is inadequate or damaged. The presence of moisture can lead to the formation of carbon disulphide, which is highly volatile and readily released at temperatures above 20oC.

Public health risk

When used as a flotation agent in the mining industry, the potential for public exposure to sodium ethyl xanthate is low. However, the compound readily decomposes releasing carbon disulphide and there may be some public exposure to carbon disulphide, particularly in the case of accidental spillage during transport. To minimise exposure to the public emergency procedures for the containment and clean-up of accidental spills should be followed.

Based on the available information and provided that appropriate controls on release are in place and transport packaging is adequate, sodium ethyl xanthate should not present a significant risk to public health.

Environmental assessment Environmental fate

Sodium ethyl xanthate used in flotation will mainly be retained on floated ore particles, and subsequently destroyed during the drying process. Hydrolysis will be the main factor determining the environmental fate of minor residues associated with the tailings. Sodium ethyl xanthate is hydrolytically unstable when exposed to acidic conditions, such as found in tailings dams.

All Australian mines currently operating concentrators have tailings dams, where effluents from flotation, spills and equipment cleaning are discharged to settle, dry and consolidate. Therefore, sodium ethyl xanthate is not expected to contaminate the Australian environment. Most of the sodium ethyl xanthate used in flotation will be retained on sulphide minerals and destroyed when these are dried after flotation. Minor residues that remain associated with the tailings slurry will be destroyed by hydrolysis in tailings dams.

Environmental effects

Little appears to be known on the avian toxicity of xanthates. However avian exposure to residues in tailings dams is not expected to elicit adverse effects as residues are low (in the order of 1 ppm) and no effect levels in rodents are two orders of magnitude higher.

Aquatic toxicity data for sodium ethyl xanthate are variable, reflecting the unstable nature of the substance. High toxicity to fish and invertebrates is evident, particularly when test organisms are continuously exposed under flow-through conditions. Mortality has been observed at concentrations extending below 1 ppm.

Environmental risk

Simple calculations indicate that xanthate levels in the tailings slurry are likely to be in the order of 1 ppm, consistent with measured values from Canadian operations. Therefore, concentrations of sodium ethyl xanthate likely to be found in the tailings slurry may be toxic to aquatic fauna. Such waste streams should therefore not be discharged to waterways.

When suitable precautions are taken to avoid entry of tailings to waterways, the environmental risk of sodium ethyl xanthate can be described as minimal in view of the low environmental exposure and limited persistence.

Risk management Hazard communication

Material Safety Data Sheets were assessed and indicated that some were below the standard considered appropriate. The data found to be inadequate in some of the MSDS were:

*

inconsistency in the United Nations number;
*

summary of the health effects had general statements with no supporting data;
*

exposure standard for carbon disulphide was expressed as threshold limit value instead of time weighted average; and
*

control measures were described by standard phrases, such as adequate ventilation instead of more specific guidance.

The labels provided in the assessment package were considered inadequate as they did not contain risk or safety phrases, first aid or emergency procedures. They complied with the requirements of the ADG Code.

Information to workers on the safe handling of chemicals is provided at induction through competency based training programs. The training programs include information on the adverse health effects of chemicals, safe handling procedures, interpretation of air monitoring results and MSDS and selection, use and maintenance of personal protective equipment.

Control measures

End users of sodium ethyl xanthate have implemented various control measures to minimise worker exposure. The control measures include isolation of the storage area, automation of the mixing process and local exhaust ventilation above the mixing tank where dust may be generated. Personal protective equipment such as chemically impervious protective overalls, long sleeve gloves, full face respirators with organic filter are worn by workers who are likely to be exposed to sodium ethyl xanthate or carbon disulphide. Workers entering the tanks for cleaning, generally follow standard operating procedures for working in a confined space and use the necessary personal protective equipment.

Emergency procedures

Most mine sites have clearly written emergency procedures and some companies have this information included in the training package for personnel. However, the fire incident at a Mt Isa mining site highlighted the failure to implement written emergency procedures even though the workers were provided with training at induction.

Packaging

According to the ADG Code, xanthates are assigned to class 4.3, that is, substances which in contact with water emit flammable gases, and Packaging Group II. Under ADG Code Class 4, substances may be packaged by any suitable method, provided that the requirements of paragraph 5.9.4 are met. According to paragraph 5.9.4, if packed in drums, then the removable head type may be used and the chemical should be packaged under an inert dry gas in a hermetically sealed container.

At least four of the incidents reported over the last two years have revealed deficiencies in packaging. Specific problems which have been encountered with the packaging are:

*

the lids of drums working loose during transportation and carbon disulphide given off; and
*

carbon disulphide release from bulker bags during transportation and storage.

These packaging problems led to the hospitalisation of several workers and in one incident the serious threat of fire to persons and property. The incidents highlight the need for a thorough investigation of packaging and in particular whether packaging meets the requirements of the ADG Code and, if so, whether there is need for change in the requirements.

Regulatory controls Exposure standard

An exposure standard for sodium ethyl xanthate has not been assigned by the National Commission, or any other country. It is not recommended that an exposure standard for sodium ethyl xanthate be developed by the National Commission.

Xanthates in the presence of heat or moisture decompose and under the conditions of storage and use the major decomposition product is carbon disulphide. The national exposure standard for carbon disulphide in Australia is a TWA of 10 ppm with a skin notation which indicates that significant absorption occurs through the skin.

Several mining sites randomly measure atmospheric levels of carbon disulphide. The limited monitoring data indicates that there were some short-term excursions over 10 ppm on a few occasions in the mixing areas. Monitoring at all mining sites was by random instantaneous sampling and an adequate and detailed assessment of exposure could not be made on the information provided.

Health surveillance

Currently the extent of health care provided to the workers in Australian mines differs at the different mines. Most mine sites have no formal health surveillance programs for workers exposed to sodium ethyl xanthate or other xanthates. No adverse health effects have been reported in workers in the data submitted for assessment except at one mine site where some contract workers complained of nausea probably due to the odour of the decomposition products.

It is recommended that sodium ethyl xanthate not be considered for addition to schedule 3 of the National Commission's National Model Regulations for the Control of Workplace Hazardous Substances as no adverse health effects are expected under the current conditions of use. However, under these regulations, employers will need to provide health surveillance in workplaces where assessment shows that exposure to sodium ethyl xanthate may result in a substance-related health effect.

Conclusion

Sodium ethyl xanthate is used widely in the mining industry in Australia as a flotation agent. The toxicological data available on xanthates, including sodium ethyl xanthate, is limited. The main health hazards of sodium ethyl xanthate are irritation of the skin and eyes and dermal toxicity. In acute oral and dermal studies the chemical causes adverse effects on the central nervous system, liver and kidneys.

Sodium ethyl xanthate readily decomposes at high temperatures and in the presence of moisture to evolve carbon disulphide. Carbon disulphide has a low autoignition temperature and is highly flammable and explosive. Carbon disulphide also produces adverse health effects.

Packaging of solid sodium ethyl xanthate presents a major risk to workers during transport and storage. To minimise carbon disulphide production, it is important to ensure packaging minimises exposure to heat and moisture. Defective packaging, such as loose lids on steel drums and loosely tied or damaged bulker bags can lead to exposure to solid xanthate and increased production of carbon disulphide. In addition, transporting the chemical in large packages, such as bulker bags, increases the risk of autoignition and flammability. Several incidents have highlighted these packaging problems. Improvements to packaging should be investigated, particularly in the use of bulker bags.

Occupational exposure during use to solid sodium ethyl xanthate and carbon disulphide is expected to be low as the process is generally isolated and automated and the chemical is used in low concentrations. The most likely areas for exposure are during the mixing process and during cleaning of storage tanks and other maintenance work. A range of control measures have been implemented to minimise exposure at the different mine-sites. The atmospheric monitoring data submitted were of poor quality making it difficult to assess the adequacy of controls.

Sodium ethyl xanthate is unlikely to present a risk to the public.

Sodium ethyl xanthate is highly toxic to aquatic fauna. Ore tailings containing xanthate residues should therefore not be discharged to waterways.

Sodium ethyl xanthate is currently unlikely to present a risk to the environment as Australian mines do not discharge ore tailings directly into waterways because of the severe detrimental consequences of such practices on stream ecology, irrespective of xanthate content.

Recommendations Classification

In accordance with the health effects criteria detailed in the National Commission's Approved Criteria and based on the information available, sodium ethyl xanthate should be classified by manufacturers and importers as 'harmful' by the oral and dermal routes and as an eye and skin irritant. Based on the classification of its health effects and in accordance with the Approved Criteria,31 sodium ethyl xanthate is considered to be a hazardous substance.

Based on animal studies, 10% solution of sodium ethyl xanthate is classified as harmful by the oral route but not a skin and eye irritant.

According to the ADG Code sodium ethyl xanthate should be classified as a dangerous good, Class 4.3, that is, substances which in contact with water emit flammable gases.

Provision of information

As sodium ethyl xanthate is a hazardous substance, employers and suppliers should be aware of their obligations to provide information, such as MSDS and labels, about the hazards of sodium ethyl xanthate. Details of these obligations, consistent with employers general duty of care, are provided in the National Model Regulations to Control Workplace Hazardous Substances.

Material Safety Data Sheets

The National Commission's National Code of Practice for the Preparation of Material Safety Data Sheets provides appropriate guidance to prepare MSDS.

A survey of the MSDS for sodium ethyl xanthate indicated that some were below the standard considered appropriate under this code of practice. It is recommended that manufacturers and importers review and upgrade MSDS in accordance with the National Code of Practice for the Preparation of Material Safety Data Sheets, and in particular ensure that the:

*

correct UN number is included in the MSDS;
*

information on the use of the chemical is provided;
*

hazardous ingredients and their proportions are listed, even if present as impurities;
*

supporting data for the health effects are stated. If no human data are available it should be stated. Animal data should be summarised and the species and route of exposure stated; and
*

summary of health effects of carbon disulphide is included as exposure is possible during use of xanthates.

Labels

The National Code of Practice for the Labelling of Workplace Substances provides standards for the labelling of workplace hazardous substances.

As all labels were found inadequate, it is recommended that labels be reviewed, upgraded and, in addition to the requirements of the ADG Code, should include the risk and safety phrases, first aid procedures, emergency procedures and reference to the MSDS in accordance with the National Code of Practice for the Labelling of Workplace Substances. Consistent with the classification the following risk and safety phrases are recommended:

Risk phrases

R21/22

Harmful in contact with skin and if swallowed

R36

Irritating to eyes

R38

Irritating to skin

R15, 29

Contact with water liberates highly flammable and toxic gases.

Safety phrases

S24/25

Avoid contact with skin and eyes.

S36, 37, 39

Wear suitable protective clothing, gloves and eye/face protection.

S3/9

Keep in a cool well ventilated place.

Training and education

Workers potentially exposed to sodium ethyl xanthate need to be trained in safe work practices to be followed in the handling, storage and transportation of the chemical. The workers should be trained in the procedures to be followed in the case of an emergency, as experience in fires in mines using sodium ethyl xanthate have shown that the fire spreads rapidly, especially when bulker bags are present. Training provided at induction should be reinforced at regular intervals, especially the emergency procedures so that workers are familiar with the procedures and can act quickly in an emergency situation.

Packaging

The most significant risk to workers and the public is through ineffective or inappropriate packaging of solid sodium ethyl xanthate, in both drums and bulker bags. Problems in packaging have led to the formation and release of carbon disulphide, causing fires and adverse health effects in humans.

Data on the self combustion of sodium ethyl xanthate&emdash;particularly on the interaction of parameters such as temperature, humidity, moisture content and package size&emdash;is not available. Therefore, it is difficult to predict situations where self-combustion may occur. It is recommended that factors affecting self-combustion should be accurately assessed by appropriate scale-down tests. These tests should be carried out by manufacturers and importers and a testing plan provided to the Director Chemical Assessment within six months of publication of this report.

The release of carbon disulphide from packages of sodium ethyl xanthate should be eliminated as far as possible. It is recommended that monitoring for carbon disulphide by the manufacturer before dispatch and by the importer on receipt of the consignment be undertaken routinely. Monitoring of carbon disulphide should be introduced as soon as possible and the results of this monitoring should be available for inspection on request. A report on implementation of this recommendation should be provided by manufacturers and importers to the Director Chemical Assessment within 12 months of publication of this report. It is recommended that the moisture content of packaged sodium ethyl xanthate is kept to a minimum. Specifications for the moisture content for each batch should be supplied by the manufacturer.

Packaging should ensure that damage does not occur under normal transport conditions and that carbon disulphide is not released during transport and storage. It is recommended that manufacturers and importers arrange with the relevant competent authority, or suitable competent person, to carry out random inspections of packaging of sodium ethyl xanthate to assess its adequacy and whether it meets the current packaging requirements of the ADG Code.

Exposure standard and atmospheric monitoring

An exposure standard for sodium ethyl xanthate has not been assigned by the National Commission. It is not recommended that an exposure standard for sodium ethyl xanthate be developed by the National Commission. It is recommended that dust levels should be maintained as low as possible in view of the dermal toxicity of sodium ethyl xanthate and the likelihood of carbon disulphide formation. A level of 1 mg/m3 as used by Dow Chemicals is considered appropriate as an operational level.

As atmospheric monitoring of carbon disulphide is currently only undertaken randomly at mining sites it is recommended that more routine procedures be carried out particularly in those areas where exposure is likely to occur such as the mixing area, storage areas, around the stock tanks and around the flotation cells. The frequency of monitoring will depend on the results obtained and can be reduced once it is has been established that control measures are effective and levels do not exceed the current exposure standard for carbon disulphide (10 ppm TWA).

Health surveillance

Sodium ethyl xanthate is widely used in Australia and is hazardous to health. However, it is considered that the chemical does not adversely affect the health of workers under the present conditions of use.

It is recommended that sodium ethyl xanthate not be considered for addition to schedule 3 of the National Commission's National Model Regulations for the Control of Workplace Hazardous Substances. Under regulations introduced in Commonwealth, State or Territory government jurisdictions in accordance with these model regulations, employers will need to provide health surveillance in workplaces where assessment shows that exposure to sodium ethyl xanthate may result in a substance-related health effect.

Environmental protection

To ensure that risk remains low, xanthate use should be restricted to well managed mining operations using tailings dams of appropriate size to prevent entry of flotation effluents to waterways. Direct discharge of xanthates or effluents containing them to waterways is unacceptable.

Incidents

It is recommended that any further incidents involving sodium ethyl xanthate be notified to the Director Chemical Assessment.

Other xanthates

The uses, adverse health effects and release of carbon disulphide and its associated hazards are similar to all xanthates. The recommendations arising from the assessment of sodium ethyl xanthate would therefore be appropriate to all xanthates.

Taken from
http://www.nicnas.gov.au/publications/car/pec/pec5/summary_report.asp

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