ACCORDING to the Food and Agriculture Organization, fish consumption globally is estimated to be 20.5 per cent per capita and is expected to increase in years to come as fish is an important source of nutrition for many people across the world, providing required protein and other nutrients such as vitamin A, calcium, iron and omega 3 fatty acids.

Throughout the Caribbean and Latin America, fish sales are consistently seeing an upward trend as this commodity is not only an important source of nutrients, but the industry in itself provides income for many people – whether they are fish farmers, fishers, or more indirectly related to the trade such as those people involved in the processing and sale of fish for human consumption.

Fish adulteration a growing public health concern

Fish, like most other proteinous food, if not handled and stored properly is prone to spoilage, yet the cost in some countries such as Jamaica ranges between $849.82 and $2,059.70 per kilogramme. In order to ensure economic gain and reduce the likehood of spoilage, it is a common practice for traders to adulterate fish with substances such as formaldehyde (formalin) – whether through the use of iced laced with formalin to disguise fish off-quality, or in some instances the fish itself is passed through a solution which is a mixture of formaldehyde (formalin) and water. Unknown to many is the fact that adulteration of fish is a food crime that poses a serious risk to the health of humans as it is estimated that 22 per cent of foods produced are adulterated every year. Cancers, renal and liver failure, and allergies in humans have all been associated with these malpractices.

Reasons why fish traders add formaldehyde (formalin) to fish

•To improve the sensory appearance of the fish

•To avoid purchasing ice which is necessary to minimise spoilage of fish due to temperature violation

• Due to the unavailability of infrastructure to preserve fish quality, such as in markets where refrigerating facilities are not available or provided for the safe and sanitary keeping of these food items.

Common health implications of excessive levels of formaldehyde (formalin) in fish

The presence of formaldehyde in fish can be naturally occurring or economically motivated, resulting in food adulteration. Excessive formaldehyde (formalin) in fish can result in gastrointestinal symptoms such as vomiting, diarrhoea, dizziness, nausea, and in more severe cases, death in people who have consumed a fish meal adulterated with formaldehyde (formalin).

How to know if fish is adulterated with formaldehyde (formalin)

Freshly caught fish has:

•Bright bulging eyes and will appear alive, even though dead.

•Slight seaweed smell, and the absence of a pungent odour.

•Hardly or no missing scales if unscaled.

•Bright-red closed gills.

•Evidence of fresh blood along the backbone.

•Fresh fish is also firm to the touch, with little or no slime.

Stale, spoilt and adulterated fish:

•Will have an off odour and, especially when adulterated with formaldehyde (formalin), the gills may be open and appear grey or off-coloured rather than bright red.

•Will appear to be dry, with a rubbery texture and hard scales.

•Eyes are white, creamy or grey.

•Body is excessively stiff

•Will show signs of spoilage such as a strong off odour.

Factors that influence fish spoilage

Spoilage of fish is due to three main factors, enzymatic autolysis, oxidation, and the action of microorganisms. Enzymatic spoilage takes place soon after the fish is caught and then dies; these enzymes are responsible for the changes that occur in the texture of the fish. Immediate storage on ice at five degrees celsius and below can retard these enzyme activities. Oxidative spoilage is responsible for change in colour, flavour, and nutrient quality of the fish and is the change that also leads to the off odour in spoilt fish. Storage of fish at temperatures of five degrees celsius, such as in the case of adding ice to the fish during transportation and storage, is advised in order to avert these changes Fish quality and safety are also affected by the growth and metabolism of bacteria in and on the flesh of the fish, and is also a reason for off quality of factors such as odour and taste.

Advice to consumers

•Buy fish from reputable sources only as fish and other seafood adulterated with formaldehyde (formalin) cannot be made safe by cooking.

•Know the signs of fresh fish and ensure that fish are kept under hygienic conditions prior to purchase.

•Seek medical attention if you are experiencing vomiting, nausea diarrhoea, stomach cramp, dizziness or any other similar symptoms after you have consumed a fish or seafood meal. In most instances these symptoms will appear within six hours or less after consuming the adulterated food.

Dr Karlene Atkinson is a public health specialist and lecturer at the School of Public Health, University of Technology, Jamaica.