Environmental Toxic Exposures and Poisoning in Children 

World Health Organization 11oct01

Main environmental and chemical threats

There is growing concern about the threats which environmental exposure pose to children's health and their development. Children do not have the biological and social protective mechanisms in-built in adults and are more vulnerable to toxicants, and pollutants (see: Children are not little adults).

From a global perspective, the Task Force on Children's Environmental Health defined the major issues of concerning children's environmental health:

1. inadequate access to safe drinking water and sanitation
2. exposure to air pollution
3. accidents, injuries and poisoning. The main health problems identified in the latter are acute exposures leading to poisoning and low-level chronic exposures causing functional impairment and developmental abnormalities during periods of special vulnerability (1,2).

Furthermore, children suffer the effects of biological and also physical threats, such as high noise levels (see section on Vulnerable groups) and ultraviolet radiation.

Many children throughout the world are still being exposed to "old" poisons such as lead, arsenic, and pesticides, some of which represent important environmental threats. They are also exposed to an increasing number of new chemicals, with poorly known toxicological effects, coming onto the market. Some of these chemicals may be present in household products and materials, in cosmetics and toys. Others appear as unexpected contaminants in food or even in pharmaceuticals. For example, children have been the main victims of counterfeit or non-quality controlled pharmaceuticals, as in the case of acute mass poisoning by diethylene-glycol contained in cough syrups (3,4) or exposure to methanol used in poultices (5). In some countries, children who from an early age, work in the informal sector or in cottage industries are exposed to toxic chemicals widely and unsafely used.

Chemicals of natural origin such as arsenic or fluoride in water or food toxicants may also represent a special environmental risk for children. For example, aflatoxins are incriminated not only in episodes of food poisoning but also in neonatal jaundice, immunosuppression, even prenatal death and reduced birth weight. They have been detected in cord blood and in 40% breast milk samples in Africa (6). Another example is that of symmetric spastic paraparesis ("Konzo") associated with cassava consumption and exposure to cyanide, which affects mainly children in areas of severe drought or under war conditions (7).

A number of environmental contaminants characterised by their resistance to degradation (e.g. metals, organochlorinated pesticides, dioxins and furans, polyaromatic hydrocarbons and polychlorinated biphenyls) are linked to effects on the nervous, immune, endocrine, and other systems of the developing foetus and the new born (8,9). Chronic, low-level exposure to these and other pollutants that enter the food, air, and drinking water of small children occur at home, in schools and playgrounds and have detrimental effects on their health and development. However, there are large knowledge gaps as these effects are delayed, and the cause-effect relationship difficult to prove.

Children have a special vulnerability to acute, sub-acute and chronic effects of chemicals present in their micro- and macro-environments. This demands urgent recognition, evaluation and, as necessary, action. This applies to all countries, but especially to those developing and in-transition countries, where the likelihood of toxic exposures is magnified by the unsafe use of chemicals, increased pollution and lack of awareness of or interest in environmental issues. The least developed countries, plagued by economic and social distress, suffer disproportionately: toxic effects are further magnified by the resulting malnutrition, infectious diseases and poverty (10).

Toxic Exposures in Children – Global Aspects

Epidemiological data reported by specialised units, such as paediatric hospitals and poisons control centres throughout the world demonstrate a high prevalence of toxic exposures and poisonings in children (11). However, the problem remains underestimated or even unknown in developing and in-transition countries. Existing health statistics do not reflect the real morbidity and mortality rate due to acute and chronic exposures to chemicals. In fact, both acute and chronic poisoning cases are usually recorded under a given system or organ effect (e.g. coma, hepatic insufficiency) and even if recognised as toxic exposures, they are entered under the wider term "injury", following the International Classification of Diseases (ICD-9 or the latest version ICD-10, produced in 1992).

N.B. The International Classification of Diseases is an alphanumeric coding system produced by WHO for international harmonization in the recording and coding of morbidity and mortality).

Other sources of statistical data are paediatric hospitals and intensive care units, forensic or medico-legal services and the poisons centres and related facilities (e.g. clinical information centres, analytical laboratories and Toxicology services). According to statistical data reported by poisons centres and specialised toxicology services, the frequency of toxic exposures in children is high: it may reach up to 67% of all consultations.

The characteristics and circumstances of exposure and the agents involved differ from one country to another. However, there is a common pattern in the importance and frequency of paediatric poisoning: about 40% to 65% of all poisonings occur in children according to published reports (14). Data submitted to the International Programme on Chemical Safety by poisons centres (PCs) through Annual Reports and surveys show that 13% to 65% of calls registered by the PCs, involve children. The same data sources show that a large majority of poisoning cases are accidental and occur in children aged one to four, mainly in boys.

The data provided by PCs reflect mainly acute toxic exposures, and information about "in utero" or breast-milk exposure, chronic, low-level exposure, "chemical" battering, effects of environmental pollutants or occupational exposures in children are seldom covered.

The mortality rate of poisonings in industrialised countries is fortunately low, but the resultant morbidity costs to the health services, and child and family stress may be high. In developing countries the morbidity and mortality data are insufficient or unreliable, but it has been demonstrated that poisoning by pesticides and household products, as well as overdoses with pharmaceuticals are extremely frequent among children. The case fatality rates reported in Sri-Lanka are between approximately 1% and 3.2% (12,13).

Why do toxic exposures occur in children?

Paediatricians, parents and teachers are well aware of the inquisitive nature of small children who tend to climb, open cupboards, taste products, explore fields, and eat products and berries found during their investigations. Environmental conditions related to housing (e.g. poor storage conditions, lack of hygiene), proximity to rural or urban working areas where chemicals are heavily used and closeness to waste sites contribute to the occurrence of toxic exposures. These exposures are mostly accidental and environmental and occur in small children.

Iatrogenic, intentional or occupational circumstances of exposure are less common in children, and they tend to be underreported due to the circumstances of the event. Iatrogenic overdoses occur through inappropriate medication or dosages administered to small children. Frequently cough syrups, containing central nervous system depressants and analgesics, are administered in doses such as those indicated for adults. Iatrogenia, known to happen in the medical setting but under reported, may be due to human error, but also to the fact that physicians may have to resort to guesswork when prescribing drugs for children, as there may be insufficient information or inadequate labelling of appropriate dosages. In general it affects children aged less than 2 years old, under intensive care, who are overdosed (15,16). Careless tutors, unstable or ignorant adults, unable to administer medicines in an appropriate manner or to provide a safe environment are responsible for many cases of poisoning in small children.

Intentional poisonings are rare, but an increasing number of illness induction syndrome, (formerly known as "Munchausen Syndrome") and "chemical battering" are being reported in the literature (17,18). It has also been observed that a growing number of self-poisonings occur during the early years of adolescence and that drugs of abuse are consumed intentionally at earlier ages, even during childhood in some countries (19,20).

Exposure in the workplace is known to occur in developing countries with poor supervised work regulations, where children may be bonded labourers and work under hazardous conditions, at vulnerable periods of life (e.g. below 12 years of age). They are involved in the informal work forces or in cottage industries. Reports on children's exposure to mercury among gold washers, pesticides in the fruit-growing industry and solvents in shoe cleaners have been published (21).

Types of chemicals involved in child poisoning

The chemicals most commonly involved in paediatric poisoning are commercial products, pharmaceuticals and natural toxins (plants) available in the home and surroundings. Sedatives, cardiotonic drugs, iron pills and analgesics are the most common cause of poisoning with pharmaceuticals. Acetaminophen is the most commonly ingested drug either accidentally by toddlers or intentionally by adolescents (in suicide attempts), and poisoning may be life threatening.

Traditional medicines are widely used in some parts of the world. Although, they tend to be innocuous plant preparations, inappropriate dosages or non-quality controlled formulations pose a risk of poisoning. For example, Aconitum drops used as cardiotonic in some Eastern European countries produces severe cardiovascular and neurovegetative effects in children. A powder called "surma" or "kohl" (eye cosmetic), applied to the umbilical cord of new-born babies, in the belief that it provides protection and avoids infection, has produced severe saturnism when contaminated with lead (22).

The most dangerous household products are bleaches, strong detergents and oven cleaners containing sodium hydroxide, which if ingested, produce corrosion of the digestive tract followed by painful, serious sequelae. Repeated surgery and years of rehabilitation are required for a child who inadvertently ingests a drain cleaner or crystallised caustic soda found in the kitchen. World-wide, the most commonly ingested (and inhaled) product is kerosene, which may produce chemical pneumonitis, secondary infection and eventually, respiratory failure in children (13, 23). Other household products ingested but fortunately less toxic are window cleaners, stain removers, shampoos and cosmetic products.

Among the industrial products, solvents (in cleaners and spot removers) are those most frequently ingested by children. However, what is most serious is their increasing intentional abuse as an inebriant by young adolescents, who may suffer irreversible damage to the central nervous system.

Pesticides such as insecticides, herbicides and rodenticides are accessible to children in rural areas, but may also be found in urban areas, by toddlers exploring their home, garden sheds or garages (24,25). A study conducted in Canada showed that 58.2% of poisoning cases registered at a paediatric hospital were due to pesticides and that the effects of most pesticides were acute and severe (26). In developing countries, the real incidence of pesticide poisoning is difficult to assess, but is known to be high, as children are frequently involved in the informal work sector and prepare and apply pesticides (27). Pesticides in house dust and their residues in food are a matter of great concern in industrialised countries, where studies have proved their contribution to the daily intake in toddlers and infants.

Potentially toxic plants (usually their berries, seeds and leaf fragments) are attractive to small children. Ingested in small amounts, they produce only transient, gastrointestinal effects. However, if vomiting and diarrhoea are prolonged, as in the ingestion of Ricinus communis seeds, severe dehydration imposes the need for hospital admittance and vigorous treatment measures. Poisoning by the mushroom Amanita phalloides may result in hepatic toxicity and death in children, as diagnosis is usually overlooked and delayed.

Snake bites and scorpion stings represent a serious public health problem in some specific geographical regions, whilst bee stings are common all over the world and may also have severe consequences. Adults and children are equally affected by envenoming according to existing statistical studies, but the effect of some venoms (e.g. scorpionic) tends to be faster, more intense and severe in small children, who suffer significant cardiac complications (28, 29, 30).

The role of Poisons Centres in Children's Environmental Health

In recent years, the concern of paediatricians, public health authorities and scientific bodies has been raised by chemicals in the environment and their proven – or potential - effects on children's health (31, 32, 33). Chronic and/or repetitive exposure to carbon monoxide, pesticide residues, lead, asbestos, chemical contaminants found in water, air and food and endocrine disrupters produce adverse effects on the health and development of children. However, the magnitude of the problem and importance of their effects are difficult to assess in some parts of the world.

Poisons Centres (PCs) have in many cases, played a critical role in the identification, management and prevention of these types of exposure. There are approximately 270 centres in 75 countries, (Yellowtox at http://www.intox.org/) providing toxicological information, medical treatment and analytical support for the management of toxic exposure cases, generally on a 24-hour-basis. They collect and analyse statistical data on toxic exposures in children and adults, as a basis for surveillance and for developing prevention and toxicovigilance activities. Most centres have paediatricians as part of their staff, or are closely related to paediatric units. Although they have addressed mainly the area of acute toxicology, most centres have growing experience on the more chronic health effects of chemicals in the environment.

Poisoning by lead is the most representative example of an environmental pollutant which produces initially, surreptitious effects, but ends up impairing children's learning abilities, behaviour, health and development, and even causing death. Poisons centres have long-standing experience in lead poisoning: most of them are involved in establishing the diagnosis, providing the chelating agents required, the specialised treatment and follow-up, and in recommending environmental control measures.

Both chronic and acute poisoning by carbon monoxide (CO) is a cause of concern to the health of children. Carbon monoxide is the most "lethal" agent in European countries. It is a foetotoxic and teratogenic agent, leaving severe neurological sequelae in many of those who survive severe exposures. A surveillance system established in the North of France (covering Nord-Pas de Calais-Picardie) showed that over 95% of all poisoning cases were accidental and the large majority occurred at home during winter months (86%) or during fires (7%), affecting entire family groups, and especially their children. In one year, 12 out of 1047 cases died and two were left with permanent sequelae. The long-term consequences of exposure are being assessed (34).

The two examples of lead and CO exposure demonstrate the relevant role of PCs in the identification, assessment and surveillance of health problems related to chemicals found in the indoor and outdoor environments of children.

A number of well-established centres and toxicology services are now providing advice and treatment in cases of chronic and environmental exposures affecting both children and adults. In response to the growing number of requests from physicians and the public in general, many centres collect information and provide advice on environmental health issues. For example, the PC in Zurich reported the provision of advice on environmental health problems due to gases, vapours, smoke and particulate material present in homes and in the workplace, as well as on issues related to toxic waste and to water pollution. This represented 16% of their inquiries in 1995 (35).

Poisons Centres are also requested to provide advice with increasing frequency on issues concerning toxic exposures during pregnancy and lactation, in response to the request from professionals and the general public about the effects of pollutants on the foetus and new-born.

However, statistical data about health effects of environmental pollutants is not recorded on a routine basis by most PCs, as they have been traditionally involved in the response and management of acute toxic exposures. Only chronic exposures to selected chemicals such as lead, carbon monoxide, mercury fumes, organophosphorus pesticides, hydrocarbons and also to toxic wastes are diagnosed and managed by poisons centres and toxicology services. In view of their long-standing experience on the health effects of chemicals their institutional setting and the multi-disciplinary human resources available, have great potential to become proactive partners in the area of children's environmental health. In some countries, such a new role would be further encouraged by the fact that an increasing number of hospital and emergency personnel because knowledgeable in the diagnosis and management of acute toxic exposures and have direct access to toxicology databases. PCs are therefore consulted only when advice is required on extremely severe or rare clinical cases. As a result, the roles of PCs could start evolving towards the provision of advice, the management and the research on environmentally-related toxic exposures and their long-term effects on human health.

Poisons Centres and related units are in a strategic position to play a potential "sentinel" role in children's environmental health. New PCs are being established in developing countries, and joining the existing ones through networking arrangements that facilitate interaction and communications. Most centres interact with health authorities and the academic sectors, are staffed by professionals with experience in toxicology and related sciences, and are becoming involved in environmental health issues. As more PCs are able to record acute and chronic toxic exposures in children in a harmonised manner, using controlled vocabularies and definitions, the compilation of a large database including diseases of environmental origin is feasible. The analysis of such a database will help assess the burden of disease and collect the evidence for planning interventions. PCs are called upon to play a more proactive role in raising awareness about CEH and contribute to research, information dissemination, training and other activities required for the protection of children's environmental health and development.

Activities of the International Programme on Chemical Safety (IPCS)

The IPCS aims to strengthen the capabilities of Member States to implement effective chemicals safety programmes, including the development of human resources and training. A number of activities have been developed in the areas of risk assessment and management, and prevention and treatment of toxic exposures (http://www.who.int/pcs). Many are of relevance to the protection of children's environmental health and development.

In the area of risk assessment, IPCS is improving the methodologies for assessing health impacts in children due to environmental exposures.

Two updated Environmental Health Criteria (EHC) documents are in preparation: Principles and Approaches for Assessing Human Reproductive Toxicity (update of EHCs 30 and 59) and Principles and Approaches for Assessing Human Neurotoxicity. A global on-line inventory of on-going research on endocrine disrupting chemicals has been established and an IPCS Global Assessment of the State of the Science of Endocrine Disruptors is in preparation, (http://endocrine.jrc.ei.it). The IPCS is co-operating with the WHO European Centre for Environment and Health, Bilthoven Division, in conducting studies periodically to assess the level of polychlorinated disbenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) in human milk.

Educational and prevention material prepared include: IPCS Posters ("Let the World Breathe", "Children at Risk", "Acceptable Daily Intake"), the publication on Hazardous Chemicals in Human and Environmental Health (WHO, 2000) and one on the Prevention of Toxic Exposure: Education and Public Awareness Campaigns (in preparation). In order to support the setting up of poisons centres and related services (clinical, information, analytical, prevention, and other) Guidelines for Poisons Control (WHO,1997) has been published in hardcopy and is also available on the IPCS INTOX CD-ROM. In the area of preparedness and response to chemical accidents, a Manual on the Health Aspects of Chemical Accidents has been published.

Training courses dealing with the diagnosis and management of toxic exposure are implemented regularly at the country and regional level, and include the consideration of toxic effects in children. A Handbook on the Management of Poisoning (WHO,1997) has been published in hardcopy and on the IPCS INTOX CD-ROM.

In order to support national programmes for the prevention and treatment of poisoning, the IPCS has prepared a Poisons Information Software for Developing Countries (INTOX). The INTOX Project of IPCS aims to support national programmes for prevention and treatment of poisoning and for response to chemical risks (http://www.intox.org/). Evaluated information on the characteristics of chemicals, and how to diagnose, treat and prevent acute and chronic toxic exposures is prepared in the form of Poisons Information Monographs (PIMs). Clinicians, toxicologists, and pharmacists from different countries assist in the preparation and review of these monographs, which are then published, translated into English, French and Spanish, and distributed to specialised units in the countries. The INTOX software will provide a mechanism for toxicovigilance through collecting comparable observational data on toxic exposures. This helps to assess existing toxicological problems affecting all population groups including children, and establish the real needs for education and prevention activities. The system has the potential of adaptation to specific need for the registration and study of environmentally-related human toxic exposures.

Priorities for Action

The protection of children's environmental health is an issue of global concern but the priorities and needs vary from country to country. The major global problems are lack of access to safe drinking water and adequate sanitation, and indoor/outdoor air pollution. These are dealt with by a number of UN and NGOs on-going programmes at the global, regional and national level. A third global issue that is gaining due recognition and requires action deals with accidents, injuries and poisonings (toxic exposures) in children, an area where different sectors should co-operate.

Child labour deserves special consideration. It represents a serious problem in many countries and interventions are urgently required. WHO is exploring with the International Labour Organization (ILO) and other relevant partners, the main needs and activities for collecting harmonised, sound data on children's exposure to toxic chemicals in the informal work sector. This would help to demonstrate the magnitude of the problem, raise the attention of relevant authorities, promote prevention approaches, and support efforts for the elimination of child labour (childlabour@ilo.org ).

High priority is given in WHO to the collection of sound data and evidence on the global burden of disease (GBD) from environmental threats in children, along with a demonstration of the cost-effectiveness of intervention strategies. Initiatives are being undertaken in a pilot phase with the GBD assessment on lead, on pesticides, access to safe drinking water and other issues. Data is required from both the national and regional level, and in order to harmonize data collection, analyses and interpretation, new methodologies are being explored in this area.

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source: http://www.who.int/peh/ceh/topics_toxic.htm 8mar02