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Toxicology and associated hazards onboard chemical tankers

What is toxicity : Toxicity is the ability of a substance, when inhaled, ingested, or absorbed by the skin, to cause damage to living tissue, impairment of the central nervous system, severe illness or, in extreme cases, death. The amounts of exposure required to produce these results vary widely with the nature of the substance and the duration of exposure to it.

Acute poisoning occurs when a large dose is received by exposure to high concentrations of a short duration, i.e. a single brief exposure. Chronic poisoning occurs through exposure to low concentrations over a long period of time, i.e. repeated or prolonged exposures. Toxicity is objectively evaluated on the basis of test dosages under controlled conditions, and expressed as threshold limit values (TLVs).

Threshold Limit Value (TLV) means the "Time Weighted - Average (TWA)" concentration of a substance to which it is believed workers may be repeatedly exposed, for a normal 8 hour working day and 40 hour working week, day after day, without adverse effect. It may be supplemented by other limits.

Prevention of exposure is achieved through a combination of cargo containment, which prevents toxic fumes or liquid from contaminating the workplace, and the use of personal protective equipment (PPE).

To ensure safety on board one must adhere to the following points: Knowledge, training and strict routine. Knowledge of the cargo to be loaded, knowledge of your ship and her equipment; training in the use of safety equipment on board; strict routines in cargo handling, tank cleaning, strict routine in command and reporting, strict routine in using protective clothing etc.

It is a clear responsibility for the Owner, the master and the officers to inform their personnel about the cargoes to be carried, safety procedures etc and to arrange for the proper training.

Information should be given partly in the form of written notices combined with informal meetings with the entire crew present when new cargoes are to be loaded or when unexperienced personnel are to be signed on. Among other things the following information should be given:

i) Cargoes to be loaded; their characteristics as regards handling, pumping, toxicity, corrosiveness, first aid etc.

ii) the cargo loading plan to be posted in places where it will be clearly seen by everyone on board and at the accomodation ladder, when in port.

iii) Post cargo information cards for products to be loaded or are contained on board. For "new" products ask the shipper for safety brochures and leaflets. iv) the personal safety equipment to be used by those involved in cargo handling, pumping, sampling etc.





v) Have available on board litterature on chemical cargoes, medical advice etc,

vi) Inform in particular if the cargo to be loaded has an odour threshold which is higher than the TLV-value . Of, and that danger cannot always be sensed in advance ( e g allyl alcohol, carbon tetra chloride, etylene dichloride).

vii) Give information that most vapours are heavier than air and have a tendency to accumulate in low spaces.

Therefore work below gratings in pump rooms, cofferdams, pipe tunnels etc is extra dangerous.

viii) Never take work clothes into your cabin! Soiled clothes must be washed before being used again or in the case of toxic products, destroyed.

ix) Wash your hands before meals!

x) Give information about fire fighting methods for each type of cargo on board.

xi) Give information if the cargo is water-reactive or reactive to other cargoes on board. Give information on segregation required.

xii) For some very toxic cargoes mouth to mouth artificial breathing might be dangerous to the rescuer (e g acrylonitrile, acetone cyanohydrine).

xiii) Information must be given particularly if the cargo danger lies primarily in vapour inhalation (e g acrylonitrile, trichlorethylene) or skin contact (e g phenol, caustic soda, sulphuric acid).

xiv) State where eye washing bottles are located (deck office, at cargo manifolds on deck, in pump rooms, on fore deck etc).

xv) Insist on that nobody should work with cargo gear without anyone standing by. Have people report when going to and returning from pump rooms!

xvi) Give information if any cargo is so toxic that an escape breathing mask must be used in an emergency.


Asphyxia

Asphyxia is unconsciousness caused by lack of oxygen, and means suffocation. Any vapour may cause asphyxiation, whether toxic or not, simply by excluding oxygen in air. Danger areas include cargo tanks, void spaces and cargo pumprooms. But the atmosphere of a compartment may also be oxygen-deficient through natural causes, such as decomposition or putrefaction of organic cargo or rusting of steel in void spaces such as cofferdams, forepeak and afterpeak tanks.
Precautions to be observed before entering any such enclosed spaces .

Anaesthesia

Certain vapours cause loss of consciousness due to their effect on the nervous system. In addition, anaesthetic vapours may or may not be toxic.

Additional health hazards

Additional health hazards may be presented by non-cargo materials used on board during cargo handling. One hazard is that of frostbite from liquid nitrogen stored on board for use as atmosphere control in cargo tanks. Full advice on dealing with frostbite is contained in the MFAG . Another hazard is that of burns from accidental contact with equipment used while handling heated cargoes.


Exposure

Exposure may be either acute or chronic. With acute exposure, the victim is subjected to a one-off high level dose and the symptoms are usually immediately apparent, although there can be a delayed reaction. The damage caused may be irreversible, even with treatment. Chronic exposure is associated with a relatively low level of exposure over a period of time. Symptoms may not be apparent until many years later, which in some cases, could be over 30 years after exposure ceases. Exposure to the product may be by inhalation, skin absorption or ingestion.

Inhalation of vapour or mist is by far the most likely route for harmful substances to enter the body. The effect of exposure will depend upon the toxicity of the vapour, the level of contamination and the volatility of the product. Exposure to the vapour may cause a variety of effects that could include systemic poisoning, irritation of the nose, throat and respiratory system and even asphyxiation.

Absorption may be directly through skin contact and any physical injuries, such as cuts or abrasions, will server to increase the absorption rate. Exposure may cause skin irritation which, in its mildest form may result in dermatitis, and systemic effects.

Ingestion may be caused, for example, by accidentally swallowing a chemical when splashed by it. Some liquids have corrosive properties such that if they come into contact with the skin, they may completely or partly destroy living tissue, causing acute pain. Others, although only causing slight skin irritation at the outset, can eventually result in severe damage to the eyes and other mucous membranes.

When to use breathing apparatus ?

Usage of full face vapour mask and vapour canisters are not recommended in a hazardous situation. Breathing apparatus is to be worn for all operations where there is a risk. Vapour canisters and masks are not fully protected. The only sure way that you can guarantee the air you are breathing is safe, is to use a compressed air breathing apparatus set filled by a dedicated compressor with a clean air certificate.


Below guideline may be useful for people working onboard chemical tankers encountering toxicology and poisoning related hazards.

Handling precautions for various toxic substances

Risk with noxious liquid cargo contact

Cargo hose disconnection - Personal Safety on Chemical Tankers

Poisoning and required first aid treatment onboard





Related info:

What is inerting of cargo tanks ? How it prevents a flammable condition ?

What is reactivity of noxious liquid chemicals while carrying at sea ?

What are the most corrosive liquid chemicals transporting at sea ?

What is putrefaction process of liquid chemicals ?

What are the physical properties of chemical cargo ?

Tank cleaning fatality- case study & lessons learned

Pre-cleaning /washing of cargo tanks

Final cleaning of cargo tanks prior loading

Tank cleaning and posoning hazards

Testing of tanks and cargoes

Practical tank cleaning methods for various noxious liquid cargo

Special tank cleaning method

Determining proper tank cleaning by acid wash method

Supervision of all tank cleaning and gas freeing operations

Disposal of tank washings, slops and dirty ballast - safe method

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