Section A Questions Deck 4 Flashcards
An employer wants to use a local exhaust ventilation (LEV) system to control workers’ exposure to a hazardous gas generated during a manufacturing process.
(a) (i) Outline control options that the employer should consider before deciding an LEV system is the appropriate means of control. (4)
(ii) Outline what the employer should consider when specifying an LEV system to control this hazardous gas. (4)
(b) Other than the employer, identify TWO other persons with responsibilities in relation to an LEV system. (2)
a) i. The employer should consider the following:
To Eliminate exposure, following these steps:
- Cease use of the hazardous gas if possible.
- Substitute the gas for a less hazardous alternative.
- Modifying the process so that the hazardous gas is no longer produced.
ii. The employer should ensure the LEV system is fit for purpose by considering:
- the process in which the airborne contaminants are generated.
- the contaminants in this case gas and their hazards (i.e., How are they dangerous)
- Where the contaminant to be controlled is generated by the process, this is called the source. It is crucial that the LEV system designer understands how the source behaves in its location at the specific workplace. Depending on the process there could be single or multiple sources.
A key part in ensuring that the LEV system is designed correctly is for the employer to draw up a specification for the supplier.
(b) LEV supplier – This will be the party or parties who design and then install the LEV system for the employer.
LEV service provider – This is the test engineers (or company) responsible for examining and testing the LEV system.
Norovirus is a common cause of gastroenteritis that can spread rapidly in closed communities such as hospitals, care homes, and cruise ships.
(a) Explain how the virus is transmitted. (3)
(b) Identify the symptoms of norovirus. (3)
(c) Outline how the spread of the virus can be minimized. (4)
(a) The virus is highly contagious and easily spreads. If an infected person doesn’t wash their hands before handling food, they can pass the virus on to others. It is also possible to catch it by touching contaminated surfaces or objects.
Sufferers are usually infectious to other people whilst symptoms last, usually one to two days. The virus can survive for several days on surfaces or objects touched by an infected person.
(b) Common symptoms of norovirus infection include vomiting, diarrhea, and stomach cramping. Less common symptoms can include low-grade fever or chills, headache, and muscle aches.
(c) Avoid having persons preparing food for others while they are sick and for at least 48 hours after symptoms stop.
Have persons wash their hands carefully and often with soap and water.
Rinse fruits and vegetables and cook shellfish thoroughly.
Clean and sanitize kitchen utensils, counters, and surfaces routinely (especially those which an infected person has touched.)
Avoiding the sharing of potentially contaminated articles, such as towels, clothing PPE.
A survey of an industrial building has revealed extensive use of asbestos material.
(a) Identify where asbestos might have been used in the building. (2)
(b) Outline control measures that could help protect workers in the industrial building from exposure to asbestos. (8)
(a) Asbestos could have been used on the roof tiles (asbestos cement) in the ceiling tiles or floor tiles. It may also be found as asbestos rope or gaskets in old equipment such as furnaces, chemical pipework, or boilers.
(b) Control measures to protect workers from asbestos would be:
- To separate the processes by enclosing the areas where asbestos has been identified, such as sealing windows and placing signage for employees to enter the enclosed area.
- Ensure an up-to-date asbestos register is in place, a register keeps track of where in the building asbestos is located and the nature of the risk pertaining to the individual building.
- By bonding asbestos fibers with other materials to prevent dust generation.
- General ventilation of the working areas with clean air.
A worker in a furniture manufacturing workshop spends most of their time machine-sanding hardwood with a hand-held power sander.
Outline control measures to help protect the worker and their colleagues from the risks of exposure to hardwood dust. (10)
- Eliminate the risk by buying pre-cut or processed wood materials
- Local exhaust ventilation (LEV) is one of the most effective ways to control dust at the source. Use LEV systems to capture dust from sanding, on-tool (LEV) attachments are also an option.
- Provide a suitable industrial vacuum to remove dust from work areas.
- Minimize worker exposure by limiting the time each person spends doing dusty work.
- Advise workers to wear respiratory protection equipment (RPE) when emptying vacuum cleaner bags or collection bags – there is a potential for high wood dust exposure.
- Ensure workers wear RPE and other personal protection equipment (PPE) suitable for the task.
- Advise workers to remove work clothing such as overalls carefully at the end of the task or shift to avoid generating dust clouds.
- Provide washing facilities at work to wash off all wood dust, so dust is not taken home.
- Advise workers to wash their face and hands immediately after finishing the task and before eating, drinking, or smoking.
- wet suppression techniques during the work will also assist in supressing the dust so that it is no longer air born.
Hazardous substances entering the body through the skin can cause systemic effects.
(a) Describe the structure of the skin. (6)
Marks will not be awarded for diagrams. A description in words is required.
(b) Explain how a hazardous substance could enter the body through the skin and cause a systemic effect. (4)
(a) Skin has three layers:
The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone. And is composed of:
- The horny zone – Layers of dead cells that protect the outer surface. These are continually being shed and replaced.
- The germinal (or living) zone – the living cells that reproduce to form the horny zone.
The Dermis, beneath the epidermis, is a much thicker layer of living tissues that contains most of the interesting structures of the skin:
- Blood vessels – that supply oxygen and lose heat to the skin.
- Sweat glands – that excrete sweat (water and salts) from the blood up onto the serfuce of the epidermis.
- Nerve endings – for pain receptors, heat receptors, pressure receptors, etc.
- Hair follicles – where skin hair grows up through the epidermis, with an erectile muscle to the side of the hair follicle capable of contracting to make the hair stand erect (for thermal insulation).
- sebaceous glands – that secrete sebum (oily liquid) onto the skin surface where it suppresses bacterial growth.
The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
(b) Certain chemicals can pass through the epidermis (outer surface of the skin) both into the skin and into the body. This is sometimes called pervasion. Absorption of chemicals through the skin can occur without being noticed, and in some cases, may represent the most significant exposure pathway. Many commonly used chemicals in the workplace could potentially result in systemic toxicity if they penetrate through the skin (i.e. pesticides, organic solvents). These chemicals enter the bloodstream and cause health problems away from the site of entry.
The alternative process through the skin is, of course, injection. This occurs either where the substance is:
- physically forced through the skin, e.g. needlestick injury, compressed air injection, cut with a contaminated sharp object; or
- introduced through the epidermis where it is damaged, e.g. cuts, grazes, dermatitis chaps.
(a) Outline why it is important to measure transport (duct) velocity when assessing the efficiency of a local exhaust ventilation (LEV) system. (2)
(b) Outline the methods that can be used to measure transport velocity in an LEV system. (5)
(c) Identify other measurements that can be used to determine if the LEV system is working as designed. (3)
(a) If the airflow velocity in ductwork falls too low, particles will no longer be transported through the system and will be deposited in the duct. This the LEV’s efficiency will be compromised.
(b) Airflows in ducts can be measured using the same equipment as and technique as for face velocity. The main problem is inserting the anemometer into the duct.
Another device that provides a useful alternative due to its small size is the pitot tube. This device measures velocity pressure inside the ventilation system. i.e. the pressure caused by the movement of air in the duct. The reading is then converted to velocity using a simple formula.
The measuring head consists of two concentric tubes, one facing and one at right angles to the airflow. The tubes are connected to each side of a manometer and so measure the pressure difference between the static pressure in the duct and that generated by the airflow.
When using these instruments, it’s important to find a suitable sampling point, any such sampling point should be in an area of ducting that is free from turbulence such as a long stretch of ducting.
(c) Other measurements that can be used are:
- capture velocity,
- The pressure differential across the filter system,
- and fan direction and speed.
- Measurement of the level of contaminants in the workplace air may also give an indication of the efficiency of a system,
- as will the emission levels from the exhaust, the static pressure, and power consumption.
Sailing instructors at a freshwater sports center are at increased risk of contracting leptospirosis.
(a) Identify ill-health effects associated with leptospirosis. (2)
(b) Outline the mode of transmission of Leptospira for these sailing instructors. (2)
(c) Outline control measures the sailing instructors could take to minimize the risk of contracting leptospirosis. (6)
(a) Symptoms of the disease can be divided into three stages:
Stage I – Fever with ‘flu-like symptoms lasting about a week.
Stage II – by the start of the second week, the fever has abated, and jaundice becomes more obvious.
Stage III – in severe cases, jaundice may be present for three or four weeks, followed by a second fever lasting up to two weeks. Recovery/convalescence can take up many weeks or months.
(b) Leptospira bacteria is found in the water in which the sailing instructors work, from the urine of various animals, therefore transmission is via the bacteria entering the body through cuts, abrasions, or mucous membranes.
(c) Measures that could be taken by the sailing instructors are:
- minimizing the time they spend in the water,
- the need to report signs of rats
- cover cuts and open abrasions,
- use of waterproof dressings.
- Good hand washing before eating, drinking, or smoking
- Washing cuts and grazes immediately with soap and running water.
(a) Outline what is meant by the term ‘biological monitoring’. (2)
(b) Outline circumstances in which biological monitoring may be appropriate. (4)
(c) Outline difficulties an employer must overcome when introducing a program of biological monitoring. (4)
(a) Biological monitoring is concerned with the measurement or assessment of hazardous substances or their metabolites in tissues, secretions, excreta, or expired air.
(b)
- It is a complementary technique to air monitoring or sampling and can be used to determine if existing controls are adequate.
- when information is required on the accumulated dose in a target organ.
- when there is a specified guidance value against which a comparison might be made (such as in EH 40);
- when there is significant absorption by non-respiratory routes.
- in circumstances when there is significant reliance on personal protective equipment and where the monitoring is required by law.
(c) Concerning the practical difficulties an employer should take into account when introducing a program of biological monitoring.
- Apart from the monitoring required by statute, it would normally be conducted on a voluntary basis.
- Consequently, the informed consent of those involved would have to be obtained and their concerns overcome.
- Other difficulties include the availability of suitable facilities or a location to carry out the monitoring especially if this must be done at the end of the shift.
- the availability of specialists to carry out the monitoring for example if blood samples are to be taken.
- maintaining the integrity of samples to avoid cross-contamination and ensuring there was no possibility of cross-infection.
- maintaining the confidentiality of the individual.
- the cost involved in carrying out the exercise.
- and finally, the fact that there are few guidance values available for comparison
Outline how an occupational hygienist should determine a worker’s long term personal exposure to total inhalable hazardous dust. (10)
In determining the employees’ long-term personal exposure to the total inhalable hazardous dust, the hygienist would be expected to monitor the exposure throughout the eight-hour shift and note both the work undertaken during the monitoring and the time for which the sampling was undertaken.
A gravimetric method should be used incorporating a pump, a filter, and an appropriate sampling head such as a 7 hole, an IOM or a conical inhalable head with the head being positioned in the breathing zone of the employee.
The pump flow rate would be calibrated and noted as would the volume of air in the sample collected, and the filter weighed before and after the sampling to determine any gain in the weight.
The concentration of total inhalable dust could then be calculated by dividing the weight gain by the volume of air with the result being expressed in mg/m³.
(a) Explain how exposure to silica dust can cause silicosis. (4)
(b) The construction of a city’s underground rail line involves extensive tunneling and concrete spraying activities.
Outline controls that reduce the risk of workers developing silicosis, while carrying out tunneling and concrete spraying activities. (6)
(a) Silica is hazardous by inhalation, preventing gas exchange and makes breathing difficult. When inhaled, respirable (due to the small size of the particles) crystalline silica dust is deposited deep in the lungs and becomes trapped in the alveoli. Over time, it causes scar tissue to form (known as silicosis – very similar to asbestosis). This progressive disease leads to breathlessness and chest pain and can prove extremely debilitating.
(b)
- dampening down
- reducing exposure in the working area through management of the time workers are in the tunnel.
- Reducing the number of employees working at one time
- ventilate the area by dilution ventilation or LEV, with the need to test/maintain these systems to ensure their proper function.
- health surveillance, which should include spirometry or lung function testing.
- Appropriate raspatory PPE ensures the proper micron filtering.
- Notices and signs
- Hygiene facilities.
