Children and teenagers are more exposed to UVR and are therefore at greater risk of photodamage than are adults because they spend appreciably more time outdoors than do adults.

POPs are of major health significance because they are not easily degraded, they become stored in fatty tissues and they biomagnify up the food chain.

Dermal absorption can be a significant means of exposure to pesticides.

Data suggest that use of lindane in childhood increases the risk of brain cancer and it has also been associated with chromosomal abnormalities, behavioural changes and reproductive effects.

Great caution should be exercised in using DEET on children.

Exposures of Concern

There is limited research outlining the effects specifically on children’s skin from environmental exposures. Much of what is known comes from clinical information on the effects in adults. There is a vast number of environmental factors that can affect skin or that enter the body primarily by dermal absorption; however, here we restrict ourselves only to certain exposures from physical or chemical agents.

These exposures are important in the context of children’s environmental health as children are mostly exposed involuntarily and the degree of exposure has been largely influenced by human behaviour. For a more thorough review of other categories of exposure (including mechanical factors and biological agents), the reader is referred to Harvey and Hogan.42

Physical Factors

UV Radiation

Ultraviolet radiation in the 290 to 320 nm wavelengths of the light spectrum, the so-called UV-B rays of sunlight, is highly penetrating and is the primary exposure of concern causing dermatological changes. Acute dermal effects include erythema, sunburn, tanning and photosensitization. At the cellular level, UVR can damage DNA.

Cumulative, lifetime damage to the DNA of skin cells, especially in individuals who always burn easily, can result in several types of skin cancer. Of these, malignant melanoma is the greatest public health concern since it has demonstrated rapidly rising incidence rates and can be associated with significant mortality. Non-melanoma skin cancers (NMSC) include basal cell and squamous cell carcinomas are the most common skin malignancies and are highly treatable.

The thinner skin of a child is more sensitive to harmful effects from UV rays. Children and teenagers are also more exposed to UVR and therefore at greater risk of photodamage than are adults because they spend appreciably more time outdoors than do adults. By age 18, a given child is likely to have received up to 80% of their “lifetime” UV exposure. It appears that episodic, acute exposure to sunlight (i.e., seasonal exposure) that is sufficient to cause blistering sunburn during childhood and adolescence substantially increases the risk of melanoma in adulthood.43 Some researchers suggest that only two or more serious sunburns as a child or adolescent will increase the risk of getting skin cancer later in life.

UV exposure also adversely affects the skin’s immune system. High dose UV exposure is linked to suppression of contact hypersensitivity reactions. Lowered responsiveness of the skin’s immune system may play a role in the development of skin cancers, allergies and autoimmune diseases, and it may affect response to infectious diseases and vaccines.44,45,46 It has also been hypothesized that there is an association between immune suppression from UV exposure and increasing incidence of Non-Hodgkin’s lymphoma, although data do not achieve statistical significance.47 It is clear that there is need for further research into the implications of immunological effects from UV exposure.

There is considerable scientific literature on the links between the thinning of atmospheric ozone (from the release of chlorinated hydrocarbons, such as chlorofluorocarbons) and the consequences for levels of UV radiation that reach the skin. Increased levels of UVR appear to be particularly problematic for populations in the northern hemisphere.

A conservative estimate (from a decade ago) is that the lifetime risk of NMSC for children today has increased by 10 to 15% over what it would be without the depletion of the ozone layer.48 For this reason, public health campaigns in this country have strongly emphasized the importance of protecting infants, children and youths from excessive sun exposure as a preventive measure.

Chemicals and Metals

Dioxin and PCBs (POPs)

Dioxin and PCBs are two types of persistent organic pollutants (POPs), a class of contaminants that includes many industrial chemicals and some pesticides. These chemicals are of major health significance because they are not easily degraded, they become stored in fatty tissues and they biomagnify up the food chain. Although PCBs are not currently in use in North America, they continue to be measured in the global environment because of their chemical stability and persistence and because they are still used in several developing countries.

Dioxins are a by-product of the production of different chlorinated organic compounds, of chemical processes and of combustion. Therefore, they are constantly being added to the environment. Both PCBs and dioxins can be measured in the body fat of all Canadians. Exposure to these chemicals is more often through ingestion or inhalation than via dermal absorption. Chloracne is the most reliable indicator of exposure to dioxins and related chemicals such as PCBs. A number of other dermal effects from exposure include hyperpigmentation, hypertrichosis, increased skin fragility and vesicular eruptions on exposed skin.49  

Vinyl Chloride

Vinyl chloride (VC) is a synthetic substance used to make polyvinyl chloride, which is used in the manufacture of plastics and vinyl products. It is also a breakdown product of substances such as trichloroethane, trichloroethylene, and tetrachloroethylene.50 Because the liquid form of VC readily evaporates, exposure is most often by inhalation of the aerosolized form; however, some VC will dissolve in water and can contaminate groundwater sources and therefore be ingested from water.

While the skin is probably the least important pathway of exposure,51 direct skin contact with liquid VC causes numbness, redness and blisters. VC is, however, associated with producing scleroderma-like lesions in skin that are distinct from those caused by systemic sclerosis in that they appear as papules and plaques on the dorsal aspects of the limbs.52 VC is a known human carcinogen that is associated with changes in liver function.

Most of our knowledge of the effects of VC comes from workers occupationally exposed to levels of VC that are much higher than the general population. VC exposure for those in a non-occupational setting can come from accidental emissions or spills (into air or water) from plastics or vinyl industries, or from landfills, hazardous waste sites or contaminated well water.

Pesticides

While we generally think of exposure to pesticides as coming from inhalation, dermal absorption can be significant as well depending on the pesticide. There are many pesticides that can be freely absorbed via the skin and may produce systemic effects as a result. The degree of efficiency with which pesticides are absorbed through the skin varies. Two specific pesticides are mentioned here because they are applied in such a way that dermal absorption is highly likely. Lindane, an organochlorine type pesticide, is also one of the persistent organic pollutants that continues to be measured in the global environment and passed on intergenerationally because of its chemical stability and persistence.

Until relatively recently, lindane was the active ingredient found in common treatments for lice and scabies and it is very efficiently absorbed through the skin. Data suggest that the use of lindane in childhood increases the risk of brain cancer,53 and it has also been associated with chromosomal abnormalities, behavioural changes and reproductive effects in humans.54 Lindane is still currently registered in Canada but is the subject of special review by the Pest Management Regulatory Agency (PMRA) of Health Canada.55

The insect repellant diethyltoluamide (DEET) is easily absorbed through the skin and can be neurotoxic in heavy doses.56 There is evidence for dermal effects, including urticaria, dermatitis, blistering, scarring in workers and in children from exposure to solutions of 50 to 75% DEET.57 There have also been several clinical reports of various neurotoxic effects in children such as toxic encephalopathy and seizures from dermal absorption of solutions with relatively lower concentrations of DEET.58,59 

Once absorbed, DEET becomes distributed to all major organs and can cross the placenta as well. Over 90% of DEET is excreted within 48 hours of absorption and it does not accumulate in skin. The concern, however, is that it is commonly used on children and that they (and the developing fetus) may be at greater risk of adverse reactions compared with adults. There are over 160 DEET-containing products registered in Canada. DEET, along with several other personal insect repellents, is the subject of an ongoing review that was announced in June, 1990, by Health Canada. The US EPA's pesticide poisoning handbook, Recognition and Management of Pesticide Poisonings, states that “if used improperly…or if a very high concentration is used on children, especially repeatedly over large skin surfaces, the potential for severe toxicity exists...Great caution should be exercised in using DEET on children.”60

Hexachlorobenzene (HCB) is a fungicide no longer in use in Canada because it is a persistent organic pollutant (POP). It is resistant to degradation, it bioaccumulates and biomagnifies, and is therefore universally present in the Canadian environment. Therefore, the main exposure to HCB is through food, primarily foods with a higher fat content such as dairy products, meat, fatty fish, eggs and peanuts.61 Most of what is known of the effects of HCB exposure comes from the accidental exposure of many people in Turkey in the 1950s.

HCB was used to prevent fungal infection in wheat seedlings stored prior to planting. During a famine, people, mostly children, who ate the HCB-treated seedlings developed porphyria cutanea tarda (PCT), with its array of dermatological symptoms such as photosensitivity, hyperpigmentation and hypertrichosis, among others. (This syndrome of effects came to be called porphyria turcica because of its appearance in this specific population.) 

Many of these dermal conditions (such as hyperpigmentation, hypertrichosis and scarring) were still observed in the exposed individuals some 20 to 30 years after exposure.62 Health Canada states that HCB blood levels detected in the general Canadian population  (< 2 micrograms/L) is not likely to produce such overt health effects.63  As one might expect, given that HCB is a POP, infants exclusively breastfed under six months have the highest average daily intake of HCB compared to any other group, including sportfish consumers. However, their intake is still six times lower than Health Canada’s Provisional Tolerable Daily Intake (PTDI) of 270ng/kg bw/day.

Children, because of their smaller size and greater exploratory and hand-to-mouth behaviour, are more likely to come into direct contact with and absorb any pesticide residues present in the environment, not just those that are applied to the body. Lastly, physiologically speaking, children are generally more susceptible to the toxic effects of pesticides because of their immature stage of development.64

Metals

Although most metals do not cause dermal effects, both nickel and certain forms of chromium both can produce allergic reactions that manifest as some form of contact dermatitis. Nickel has many different uses whereby a child might be exposed, including nickel-plating in costume jewellery and earring studs, belt buckles and clothing studs. Nickel is also found in a number of household items such as cutting shears, cookware handles, paper clips and coins. Nickel allergy can produce varied reactions including vesicular dermatitis and eczema in areas directly exposed.