Industrial Hygiene Airborne Hazard

The Bhopal Disaster

By, Abirami V.Veeramani

Kong Wanying Mohd Yusri Hafizi

Nivashini Krishna KumarSiti Saidatul

Occurrence 3rd December 1984Place of occurrence

Bhopal, Madhya Pradesh, India.

Company Union Carbide Corporation.Chemical Methyl Isocyanate (40 tons)People Affected > 500,000People Died (+-) 40,000What Happened 45 tons of methyl Isocyanate (MIC)

escaped from two underground storage tanks at The Union Carbide Pesticide Plant.

What Happened ?

To The Human Health• Respiratory Disorders – Irritation to the lungs, causing

coughing and/or shortness of breathing. Higher exposure caused build up of fluids (pulmonary enema). Caused Asthma.

• Cancer Hazard – Caused mutation (genetic changes). It caused cancer.

• Reproductive Hazard – Association between exposure to Methyl isocyanate and miscarriages. It may damage the growing fetus. May also affect fertility in men and women.

• After Effect- Traces of many toxins were found in the Brest Milk of mothers and were in turn transmitted to the recipient babies.

About 550 000 people were exposed to the gas. A government affidavit (Indian Govt.) in 2006 stated the leak caused 558 125 INJURIES including 38478 TEMPORARY PARTIAL INJURIES and approximately 3900 SEVERELY AND PERMANENTLY DISABLING INJURIES

BHOPAL GAS TRAGEDY:

Union Carbide Corporation (UCC)Started in 1969 in Bhopal.

Phosgene, Monomethlyamine, Methyl Isocyanate (MIC) and the pesticide carbaryl, also known as Sevin.Taken over by DOW Chemicals in 2001.DOW refused Union Carbide’s Liabilities in Bhopal, India.

Because of SAFETY REGULATIONS WAS BEING

“Indianized”…

* Indianized: In-adequacey, underpractice, deviated.

SAFETY REGULATIONPipe Cleaning Procedure• As part of routine procedures, the pipes leading from the MIC

distillation column to the storage tanks were regularly flushed with pressurized water. MIC and any associated products can be quite corrosive and could form corrosion deposits in the pipe. These deposits would contaminate the MIC in the tanks and could initiate unwanted reactions. During cleaning, valves in the product lines were to be closed and a blank or slip-blind placed in the product line leading to the storage tank to prevent contamination.

•  • However the valves, although closed, were not sealing properly

because of corrosion and the maintenance crew forgot about the blank. It appears that about 1000 kg of water plus metal debris entered tank 610.

• Assuming all the previously described safety features were operative, this should not have been a catastrophic occurrence.

Safety• A Nitrogen line was connected to the tank to transfer the

product by inert pressurization of the headspace.

• The tank was fitted with a pressure relief valve and rupture disc. The vent line from the valve exhausted into a scrubbing tower filled with caustic soda (NaOH). This would neutralize the MIC to form Sodium isocyanate. Any residual gas from the scrubber was sent to a 30 m tall flare stack where it would be burned off.

• There was an external coiled jacket on the vessel through which coolant (freon / chloroform) was re-circulated. This was to keep the vessel contents at 0 C and thus prevent any adverse exothermic reactions occurring.

• Tanks were not to be filled above the 50 % mark so that in the event of dangerous chemical reactions occurring, solvents could be pumped in to quench the reactions.

ANTICIPATIONHazards in any large scale in any chemical processing industry can be classified into the following categories ;-

Mechanical risk Injuries to the head, limbs, eyes as a result of negligence on the part of maintenance personnel in the use of improper tools, bypassing prescribed safety procedures, neglect of personal protective wear, risk associated with machinery.

Electrical risk Which results in shock and/or burn are most often of a consequence of poor maintenance

Fire and explosion risk Due to pipe line failure, leakage from joints carrying combustible gas and etc

High/low temperature risk Burns due to contact with hot surfaces of pipeline, equipments, frostbite to exposure to extreme cold temperature

Toxic /carcinogenic chemical exposure risk

Acute toxicity due to inhalation of chemicals, irritation

Corrosive/reactive/radioactive chemical exposure risk

Severe burn, damage to eye, skin, body tissues ,etc due to contact with chemicals.

• Process of watching, observing and reviewing.

• Should performed regular basis to avoid the incident happened again

and under control.

• Identification of hazards

- Fire hazard

- High temperature and pressure

- Toxic chemical ( poisonous gases and dust )

- Electricity

- Non working of safety devices

• Maintain the records.

RECOGNITION

Evaluation of Airborne Hazard

Extend of chemical exposure at worker / workplace

Measurement / Monitoring of Hazard

Personal Exposure Monitoring Environment / Area Exposure Monitoring

Principle Approaches • Direct Reading • Lab Analysis

Airborne chemical exposure• Can be periodic or continuous and is the

quantitative or qualitative assessment of the extent of pollutants in or around the workplace.

• Compliance with appropriate legislation and to evaluate existing control measures.

• The factors in determining airborne chemical exposure are: – type of contact– length of contact– chemical concentration

Air monitoring • The purpose of an air monitoring program is to confirm

whether specific hazardous chemicals are present and to determine if the concentration presents a hazard

• Monitoring Method - Monitoring methods vary in their accuracy and specificity based on principal approach of finding airborne contaminants : – Direct reading – Laboratory analysis

Direct Reading and Laboratory Analysis

Factors Direct Reading Laboratory Analysis

Definition • As early warning device• Information obtained can be used to implement appropriate protective measures or to determine further detailed monitoring

• To determine low-level concentration of contaminants and its quantities in ambient • Data can be used to determine the initial level of worker personal protection necessary to modify field sampling procedures

Equipment / Instruments

• Photo ionization detectors • Paramagnetic • Detector Tubes

• Gas Chromatography • Spectrofluorometer

Instruments

Personal Monitoring • Done for highly-risk workers who are :

– Closest to source of chemical contaminant areas– Work practice involves handling hazardous chemical

– Exposed to hazardous chemical in stretch of TWA8

• Personal monitoring sample need to be collected in : – Breathing zone (defined as zone infront of the face within 20 to 30 cm

diameter from the nostrils) – Outside of face piece if respiratory equipment present

• Usually uses passive devices

Environmental / Area Monitoring

• Are positioned in the general area of the worker and/or operation of concern.

• This information serves as the basis for selecting the appropriate monitoring equipment and personal protective equipment (PPE) to use when conducting site monitoring.

• background measurements that can show the spread of contaminants or indicate when entry to an area may be considered safe

Monitor for IDLH

General onsite

Monitoring

Perimeter Monitoring

Periodic Monitoring

Depending on site conditions and project goals, four categories of site monitoring may be necessary:

Characterize the site

Uses variety of medium to

collect sample

Detect contaminants that might escape

from the site

Keep update on change over

time

Final Step

• Interpreting Results - The significance of results depends upon accuracy and the recommended exposure limit.

• Possible interpretations of monitoring results may be: hazardous chemical was not detected;no hazardous concentrations were detected; andhazardous concentrations were detected.

•i) Very High (RR=5) : Continuous monitoring •ii) High Risk (RR=4) : Monthly to quarterly •iii) Moderate (RR=3) : Quarterly to annually •iv) Low Risk (RR=2) : 1 – 3 years •v) Very Low (RR=1) : 3 – 5 years

CONTROL

• Eliminate• Substitute• Isolation• Engineering control• Administrative control• PPE

ELIMINATION

• Eliminate all ignition sources (no smoking, flares, sparks or flames in immediate area).

SUBSTITUTE

• Change the methyl isocyanate to alpha napthol chemical.

• Alpha Napthol is a carbonyl group addition followed by reaction with methyl amine would eventually give carbaryl.

• This process does not generate or require handling the of phosgene

• This process does not require storage of MIC• Inherently safe process.

ISOLATION

• Built the factory far from residential area.• If tank, rail or tank truck is involved in a fire,

isolate for 800 meters (1/2 mile) in all direction

ENGINEERING CONTROL• All operation involving Methyl isocyanate must be

performed under a chemical fume hood.• There must be adequate exhaust ventilation and capture

filtration.• Installed the respirator into methyl isocyanate tank. The

respirator may also used for operations which require entry into tanks or closed vessel, and in emergency situation

• Install the security alarm

ADMINISTRATIVE CONTROL

• A management representative should be nominated as responsible for personal protective equipment supply, maintenance and training.

• Give MSDS training to all employees. MSDS should be obtained for all potentially hazardous substances from the suppliers of materials before handling.

• Give emergency plan training to all employees and public.

• Provide first aid training to employees.

PERSONAL PROTECTIVE EQUIPMENT• Employer must provided with and required to use impervious

clothing, gloves, face shield and other appropriate protective clothing necessary to prevent any possibility of skin contact with liquid methyl isocyanate.

INHALATION Face mask/face shield

EYE Goggle/face shield

SKIN Rubber hand glove/safety shoes/body overclothing