Children's environmental health issues can range from those for which the weight of the evidence is substantive to many more for which the scientific basis for an association is incomplete. For example, much evidence points to a relationship between second-hand tobacco smoke and pre-term birth, asthma incidents and severity, sudden infant death syndrome, and lung and middle ear infections. Cognitive deficits have also been associated with high-level prenatal maternal methyl mercury, PCBs, ionizing radiation exposure, and childhood lead exposure. There are numerous examples of diseases where environmental links are suspected. There are also many emerging children's environmental health issues, including endocrine disruptors, pesticides, chlorination disinfection by product solvents, etc.
Researchers are only beginning to describe the nature of the association between many environmental hazards and health outcomes, as well as their interactions with other health determinants.
We also know the potential social and economic costs can be very high. One study in the U.S. found the annual costs associated with the environmental component of childhood lead poisoning, asthma, cancer, and neuro-behavioural disorders were estimated at $55 billion a year in the U.S.
A high climate of concern also exists over children's environmental health disorders, and I'll touch on this a little later.
If we think about children's health issues from a risk perspective, we want to think about the probability of the occurrence and the nature of the consequences. The probability of the occurrence is influenced by such factors as the nature, level, and timing of exposure, as well as factors influencing susceptibility. Consequences due to early life exposure, along with the development of body systems, may lead to serious, permanent, and long-lasting effects and even death.
The nature of children's environmental exposure is very broad. A number of exposures must be considered.
An exposure that was talked about earlier was breast milk and in utero exposures that are specific to the developing child. We know breast milk is a particularly unique exposure for children and has been found to contain pesticides and plasticizers, among other chemicals.
We must also consider workplace exposures, as parents often bring home these exposures to the child at home. Children have greater contact with their physical environment through crawling and hand-to-mouth contact. These unique differences greatly increase the amount of environmental exposure received.
The increased susceptibility of children due to immature systems is also great. We must consider the critical periods of development for various structures. For example, the lung and reproductive systems are two systems that have been highlighted in the literature. For the reproductive system, as an example, there are many critical exposure time windows during the fetal period, as well as after birth and into adolescence. The child may experience much greater levels of environmental exposure. For example, the respiratory ventilation rate of an infant is approximately 133 millilitres per kilogram per body weight, while that of an adult is only two.
Another example is drinking water. Infants consume nearly double the amount of drinking water per kilogram per day compared to an adult. Similar examples can be found for fruit consumption and soil ingestion.
Another important consideration is the possibility that some groups of children may be more highly susceptible to environmental exposures than average. One example we can think of is possibly the aboriginal population. The aboriginals in the Canadian Arctic have undergone much study through the northern contaminants program. They represent a population in which much greater levels of environmental exposures are found. For example, levels of maternal blood mercury in the Inuit population are much greater compared to other aboriginal groups in the north or Caucasians living in the north, as well as people living further south in Canada.
Last, if we think about the consequences, there are many examples we can think of. One example is lead exposure. In the U.S. the economic losses associated with a decrease in lifetime earnings due to blood level exposure has been estimated at over $27.8 billion for boys and over $15.6 billion for girls annually.
The last point I'm going to make is risk perception. Risk perception is an important component of risk management decision-making.
Through a national survey we conducted, we know that Canadians have a high level of environmental concern. We also know that risk issues associated with certain populations, including children, tend to be perceived as higher. Many of the children's environmental health issues have delayed effects, are newer to science, and have received much mass media attention. All these factors, including many others, tend to increase the levels of risk perceived by the public.