What is the route of entry called when a hazardous substance enters the body through the mouth?

A. ROUTES OF EXPOSURE

Exposure to chemicals may occur by the following routes:

1. inhalation,

2. ingestion,

3. contact with skin and eyes, or

4. injection.

1. INHALATION

Inhalation of toxic vapors, mists, gases, or dusts can produce poisoning by absorption through the mucous membrane of the mouth, throat, and lungs and can seriously damage these tissues by local action. Inhaled gases or vapors may pass rapidly into the capillaries of the lungs and be carried into the circulatory system. This absorption can be extremely rapid. The rate will vary with the concentration of the toxic substance, its solubility in tissue fluids, the depth of respiration, and the amount of blood circulation, which means that it will be much higher when the person is active than when he or she is at rest.

The degree of injury resulting from exposure to toxic vapors, mists, gases, and dusts depends on the toxicity of the material and its solubility in tissue fluids, as well as on its concentration and the duration of exposure. Chemical activity and the time of response after exposure are not necessarily a measure of the degree of toxicity. Several chemicals (e.g., mercury and its derivatives) and some of the common solvents (benzene) are cumulative poisons that can produce body damage through exposure to small concentrations over a long period of time.

2. INGESTION

Many of the chemicals used in the laboratory are extremely dangerous if they enter the mouth and are swallowed.

The relative acute toxicity of a chemical can be evaluated by determining its LD50, which is defined as the quantity of material that, when ingested or applied to the skin in a single dose, will cause the death of 50% of the test animals. It is expressed in grams or milligrams per kilogram of body weight. In addition, many chemicals may damage the tissues of the mouth, nose, throat, lungs, and gastrointestinal tract and produce systemic poisoning if absorbed through the tissues.

To prevent entry of toxic chemicals into the mouth, laboratory workers will wash their hands before eating, smoking, or applying cosmetics; immediately after use of any toxic substance; and before leaving the laboratory. Food and drink may not be stored or consumed in areas where hazardous chemicals, radioactive materials, or biohazardous materials are being used. Chemicals should never be tasted; and pipetting and siphoning of liquids should never be done by mouth.

3. CONTACT WITH SKIN AND EYES

Contact with the skin is a frequent mode of chemical injury. A common result of skin contact is a localized irritation, but an appreciable number of materials are absorbed through the skin with sufficient rapidity to produce systemic poisoning. The main portals of entry for chemicals through the skin are the hair follicles, sebaceous glands, sweat glands, and cuts or abrasions of the outer layers of the skin. The follicles and glands are abundantly supplied with blood vessels, which facilitates the absorption of chemicals into the body.

Contact of chemicals with the eyes is of particular concern because these organs are so sensitive to irritants. Few substances are innocuous in contact with the eyes; most are painful and irritating, and a considerable number are capable of causing burns and loss of vision. Alkaline materials, phenols, and strong acids are particularly corrosive and can cause permanent loss of vision. Also, eyes are very vascular and provide for rapid absorption of many chemicals.

Skin and eye contact with chemicals should be avoided by use of appropriate protective equipment.

In the event of skin contact, the affected areas should be flushed with water and medical attention should be sought if symptoms persist; in the event of eye contact, the eye(s) should be flushed with water for 15 min and medical attention should be sought whether or not symptoms persist.

4. INJECTION

Exposure to toxic chemicals by injection seldom occurs in the chemical laboratory. However, it can inadvertently occur through mechanical injury from glass or metal contaminated with chemicals or when chemicals are handled in syringes.

B. Laboratory Specific Operating Procedures

Place laboratory specific operating procedures for working with particularly hazardous substances, here. (See Appendix J for guidelines on developing SOPs)

Inhalation is taking in hazardous chemicals into the body by breathing them in. The chemical contaminants are breathed in through the nose or mouth and reach the lungs. From the lungs, the chemical contaminants such as mists, dusts, fumes, gas and vapors are conveyed to the bloodstream and tissues.

So, how does inhalation of hazardous chemicals occur?

Firstly, the air in the workplace is contaminated by the hazardous chemical in the form of vapors, mist, dust or fume.
The worker breathes in contaminated air through the nose and/or mouth.
Air breathed in via the nose is filtered by nasal hairs to remove large, solid contaminants. But because of the small bones and cartilages of the nose, the inhaled air will swirl around the nose and some large particles will be trapped in the mucus lining of the nose.
Next, the air from the mouth and nose will pass through the back of the throat and will gain entry into the pharynx (the entrance to airways). The pharynx is divided into two: the trachea leading to the lungs and the esophagus leading to the stomach.
The contaminated air will enter the trachea. The trachea is divided into two large branching tubes called bronchi. Each tube, called bronchus, enters one lung and then begins to divide into smaller and tinier tubes called the bronchioles.
The bronchioles end in thin-walled air pouches called alveoli (singular-alveolus). Alveoli walls are supplied with blood capillaries which bring carbon dioxide from the body to the lungs for exhalation (breathing out) and collects contaminated air (oxygen) from the lungs for distribution throughout the body.
Hazardous vapors, mists, fumes or gases that reach the alveoli will pass into the bloodstream and be distributed around the body, resulting in adverse effects.

Examples of hazardous chemicals that enter the body through inhalation include:

Vapors and Gases: When organic solvents such as methyl ethyl ketone (MEK), toluene or alcohols evaporate, they produce vapors which may contaminate the air in the workplace. Similarly, workplace chemicals that exist as gases under pressure may also diffuse in the workplace when their containers are opened.

Mists: Various industrial processes can produce tiny liquid droplets which float in air as mists. Usually, the mists form when liquids are broken up, splashed or atomized, but some also form when gases condense into tiny liquid droplets. Examples of workplace mists are paint spray mists formed during painting operations, oil mists formed during cutting and grinding, and acid mists formed during electroplating.

Dusts: Are tiny solid particles generated by abrasive or mechanical workplace activities. The solid particles are light enough to float in air, but they can also settle to the ground after a period of time, resulting in dusty surfaces.

Fumes: Fumes are extremely tiny solid particles produced when heated metals are evaporated in air and then cooled back to solid. They are commonly produced in welding operations and remain airborne, contaminating workplace air.

Smoke: Smoke is soot or carbon that is produced when organic chemicals or substances burn. The smoke particles may remain in the air long enough to contaminate workplace air, but can also settle down to form black coloration on equipment surfaces.

Where there is a COSHH risk present in a place of work, a number of extra precautions need to be taken to prevent the hazardous substance from entering the body.

One precaution involves the consumption of food. A number of workers will be tempted to have lunch or a snack but either forget or deliberately choose to not wash their hands before handling food. If they have been working with a hazardous substance, this may still be present on their hands and be transferred onto the food before it is eaten and ingested. Even if the person has not been involved in the handling of the substance, they may still have gotten it on their hands from touching objects such as door handles which have been touched by others who have. Examples of such COSHH risks include paint, chemical cleaners and petrol. In fact, petrol and chemical cleaners will be particularly hard to detect as they will be practically invisible, unlike paint which should be easy to detect on a hand or door handle.

To combat this risk of COSHH contamination and accidental ingestion, workers should be made aware through suitable COSHH courses of the necessity for taking precautions such as washing hands after handling substances and before touching food. They should also be fully informed before starting work of the dangers posed by the substances they are working with, as well as the welfare facilities in place.

It is important that workers understand that COSHH related illnesses and conditions may not show up for many years or late into a person's life. Exposure to hazardous substances over time, even those considered low-risk and in small quantities, can build up over time until the damage becomes irreversible, so whilst some instances of a substance being consumed may not do any damage, if it becomes a regular occurrence over the course of a person's working life, it may be too late to reverse the consequences.

How Can Hazardous Substances Enter the Body?

Hazardous substances are present in some form in virtually every place of work. COSHH - the Control of Substances Hazardous to Health - regulations aim to protect workers from suffering short-term or long-term ill health through working with hazardous and harmful substances. Whilst the danger and level of hazard will vary depending on the particular industry, even what are considered low risk working environments will almost certainly contain some sort of COSHH risk such as cleaning fluids like bleach.

Hazardous substances can take a variety of forms, which obviously affect how the particular substance can enter or have an effect on a person's body. A COSHH risk assessment should not only determine which hazardous substances pose a risk to health, but also to identify how these particular substances can enter the body, so that remedial action can be taken to prevent harm occurring.

Although there are a number of methods and routes of entry for a person to acquire a harmful substance into the body, the three main ones are:

Inhaling:- Breathing in a hazardous substance is the most common route for a hazardous substance to enter the body. Substances such as harmful fumes, organic contaminates like fungi or bacteria, or inorganic particles like dust can all be inhaled, where they enter the lungs, causing damage to them, or are absorbed into the bloodstream where harmful toxins can be spread around the body, causing potential damage to organs.

Absorption through the skin:- This method of entry occurs when the substance in question comes into contact with the skin and enters the body through an open wound or through the pores of the skin.

Ingestion:- Although not as common as the other two methods listed above, substances which are harmful to health can also be ingested through the mouth either by breathing in dust particles through the mouth, or by accidental swallowing (e.g. a hazardous substance on the hands which was not washed off before handling food).

Injection:- Accidental injuries caused by sharp objects can penetrate the skin and allow harmful substances into the body. Particular hazards include discarded needles and syringes. There are numerous occupations where sharps risks are present including customs officials searching luggage, waste disposal workers (either medical waste or household), and construction workers where illegal drug use may have taken place on abandoned or derelict sites, or even current building sites if there have been trespassers on site overnight during the construction work.

Once harmful substances have entered the body, they can cause damage to one or more of the body's systems, depending upon the type of substance in question and its particular properties. The systems of the body that are most at risk are the respiratory system, the cardiovascular system, the nervous system and the urinary system.

As with most risks, prevention is a much more preferable option than dealing with the consequences. For this reason, it is vital that your employees receive suitable COSHH training which covers the particular substances that they will be working with or around during their workplace activities. COSHH training should therefore form a part of your programme of health and safety training, including managers and supervisors being able to perform a sufficient COSHH risk assessment.

The Need for Safe Storage of COSHH Hazards

Substances which are hazardous to health are not only a danger when they are being used; they can also pose just as much of a risk whilst they are being stored. Incorrect, unsuitable or improper storage of hazardous substances can result in leaks, spillages and contamination, not to mention possible explosions and fires.

In fact, it is not uncommon for the results of leaks or other breach of containment to cause far more wider-reaching and destructive consequences to health than using the actual substance on its own normally could ever cause.

For these reasons, the safe and proper storage of hazardous substances is of paramount importance. Not only will storing hazardous COSHH substances safely help to prevent harm from coming to a person, but it will also serve to reduce potential damage to the environment that would occur if, say, oil were to leak out and contaminate the groundwater and surrounding waterways.