General principles

The diagnosis of poisoning may be simplified if one or more of the following factors indicate the probable cause:

• the circumstances of the incident, for example, a leakage of chemicals;
• the nature of the illness and its timing in relation to recent exposure to chemicals;
• epidemiological factors, for example, when more than one person is affected and all develop a similar illness.

However, it must be understood that:

• the effects of some poisons resemble those of natural illnesses, such as vomiting, diarrhoea, or collapse;
• the presence of chemicals on a ship does not necessarily mean they are the cause of the illness (this is unlikely unless there is clear evidence of leakage);
• individuals may be exposed to the poison at different times or to varying degrees, and may therefore become ill at different times or with varying severity;
• individuals respond differently to poisons depending on their health, physical condition, and level of exposure.

In a typical case of poisoning, three stages of illness may be identified: latent, active, and late.

The latent stage

This is the period between the entry of the poison into the body and the appearance of the first symptoms or signs. These usually appear quickly after exposure, but in some cases there may be a delay of several hours.

The active stage

This is the stage during which the signs and symptoms of poisoning are clearly evident. Many different chemicals can produce similar symptoms, so treatment is generally applied in a broad manner.

General symptoms of poisoning include:

• headache
• nausea and vomiting
• drowsiness
• changes in mental behaviour
• unconsciousness
• convulsions
• pain

Signs of severe poisoning include:

• a rapid and weak pulse
• grey or bluish skin colour
• severe difficulty in breathing
• prolonged unconsciousness

The late stage

In most cases, symptoms resolve within a few hours, especially if exposure is minimal. However, if a large amount of a toxic substance has been absorbed, exposure has been prolonged, or the chemical is highly toxic, symptoms may persist for hours or even days.

The patient’s condition may worsen due to complications, most commonly:

• suffocation
• bronchitis
• pneumonia
• pulmonary oedema
• heart failure
• circulatory collapse
• liver failure
• kidney failure

For detailed information on specific toxins, their symptoms, and treatment, refer to the Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (Chemicals Supplement).