Relevant information should be obtained about the child's home environment and neighborhood. For example, it is important to find out the following information:
type and age of the child's home,
whether the home was recently remodeled,
history of previous industrial use of the property,
water source and heating system used in the home,
any use of household chemicals (e.g., pesticides),
occupations of adults in the home (e.g., the mother or father could bring hazardous materials home from work on clothes or shoes),
hobbies of household members,
herbal medicine consumption by anyone in the home, and
whether any rituals that use mercury are conducted. (Some ethnic traditions encourage sprinkling of mercury around the house for religious reasons. Mercury or azogue is sold at shops or botanicas.)
Questions should also be asked about child care arrangements (e.g., type, condition, and age of the facility; location; habits of the caregiver [e.g., smoker or nonsmoker]; commonly used play areas; outdoor activities; and other potential sources of hazardous exposures to chemicals) (Table 4, Table 5, and Appendix C). In most cases, the interview alone will be sufficient to gather the information needed to assess the potential for hazardous exposures at home. Data collected by interview can then focus biologic testing to consider an environmental etiology of the presenting problem.
The interview and the results of clinical laboratory assessments will direct where focused evaluation of the child's environment is needed. If an environmental cause of a syndrome is strongly suspected, but no obvious source is identified by interview or clinical examination, a house call by an environmental assessment specialist might be indicated to determine the potential for hazardous environmental exposures.
The patient's problem list is as follows: anorexia and weight loss; irritability and photophobia; weakness; pruritic rash on trunk and face; peeling, erythematous rash on hands and feet; and mild hypertension.
The differential diagnoses for a 2½-year-old child who has new, but insidious, onset of behavioral change with irritability; photophobia; anorexia; and an excoriated papulovesicular rash on his trunk and face, with sweaty, pink and scaling skin on his hands and feet, include the following:
Because of the relatively long history (1½ months) of symptoms, the likelihood seems small for most infectious diseases. The history of normal growth, diet, and past use of multivitamins with iron makes the likelihood of a primary nutritional deficiency remote. CNS degenerative conditions do not show up with rash; then again, the rash on the trunk and face could be unrelated to the child's refusal to walk. Metabolic disturbances cannot yet be ruled out, but they do not include photophobia. Psychosocial disturbances could be a consequence rather than a causal actor. Leukemia, collagen vascular diseases (e.g., JRA), acute rheumatic fever, vasculitis (e.g., Kawasaki syndrome), and intoxications also cannot yet be ruled out.
From an environmental/medical point of view, possible sources of intoxication include exposure to heavy metals such as lead and mercury. The distinctive dermatitis of hands and feet, along with CNS symptoms, suggest
acrodynia, a form of childhood poisoning usually due to chronic elemental or inorganic mercury intoxication. Acrodynia develops after the mercury volatilizes or oxidizes, or both. In acrodynia, also known as "pink disease," the hands and feet are described as puffy, pink, paresthetic, perspiring, and painful.
Note: This is not a comprehensive listing of all differential diagnoses a health care provider would or could consider for this case scenario. The list should be used as a working guide only.
Without prompting or experience with a recent evaluation of a case of pediatric mercury poisoning, a pediatrician or family physician is not likely to include environmental exposure as a primary or even secondary consideration when elaborating a differential diagnoses on the basis of the clinical picture presented. More than likely, the baseline tests ordered would include
white blood cell count with differential;
blood smear;
electrolytes, with blood urea nitrogen and creatinine;
a computed tomography scan of the brain to rule out degenerative changes or a space-occupying lesion; and
a spinal tap (after risk for herniation has been excluded).
For those health care providers alert to environmental etiologies, screening for heavy metals (e.g., blood lead and urine mercury) in spot urine would be ordered.
Urine tests provide the best estimates of the current body burden of chronic mercury poisoning. Elemental and inorganic mercury are mainly excreted in the urine. Laboratory confirmation of exposure to elemental and inorganic mercury can best be obtained by measuring the level of total mercury in a 24-hour urine collected in an acid-washed container. A first morning void can provide reasonable accuracy if the sample is adjusted for concentration of urine by using urine creatinine or specific gravity. Blood mercury levels reflect mainly recent elemental and inorganic mercury exposure (i.e., within 5 to 7 days) and correlate poorly with clinical effects. Appendix B has more information about lab testing and elemental mercury.
Also, for many acute known exposures, when or if the child is very ill, or for unknown exposures, when the child's signs and symptoms do not follow a usual pattern, consultation with hospital emergency room physicians, pediatric intensive care specialists, medical toxicologists, and/or environmental medicine specialists should be considered (e.g., PEHSUs).
The child and grandmother have evidence of exposure to elemental and/or inorganic mercury at the following levels: 321 and 37 µg/g creatinine, respectively. The father and the mother have lower levels of exposure (18 and 12 µg/g creatinine, respectively). This pattern of mercury exposure suggests that the child's and grandmother's exposures are occurring at home, where both spend more time than either parent.
Three possible explanations should be considered. First, the father, who is almost certainly exposed to mercury in his work, might be bringing mercury home on his shoes or clothing, which has subsequently contaminated the rugs and volatilized at room temperature. Second, mercury might have been spilled recently in the family's home (a) by the teenager who cleans the home and who was involved with taking mercury from the chemistry lab, (b) by a broken thermometer or other mercury-containing instrument, or (c) as a result of a family hobby (e.g., cosmetic products or metallurgy); this mercury might have volatilized after exposure to room temperature. Third, mercury might have been spilled at some earlier time, when the building in which the family lives was used for commercial activities, and might be continuing to undergo subsequent volatilization. In any case, a 2½-year-old boy spends considerably more time playing closer to the floor than an adult does; thus, the boy will be exposed to the volatilized mercury.
About 30% of interior latex paints manufactured before 1990 contain mercury compounds that might volatilize at room temperatures. Although paint manufacturers voluntarily removed mercury from latex paints in August 1990, many people keep partially used cans of old paint for repainting. Therefore, pre-1990 paints might continue to be a source of mercury exposure. In this case, however, paint is an unlikely contributor to the mercury contamination because significant mercury exposures occur shortly after the application of mercury-containing paint (Aronow et al. 1990), and this home was not painted recently.
Levels of ambient mercury should be measured in the home. Such testing and related assistance can usually be obtained through local or state public health officials. In some communities, poison control center professionals can facilitate appropriate testing of the home environment. Other sources of clinical toxicologic information and technical assistance include ATSDR and EPA (Appendix D).
Information should also be gathered about possible take-home contamination from the father's workplace. The child health care provider and/or pediatric environmental medicine specialist might interview the father and also talk to a safety officer at the thermometer factory. MSDSs, listing hazardous agents used in the factory, should be requested by the child's father or the child health care provider. Because elemental mercury used in the manufacture of thermometers adheres easily to work clothing, work practices at the factory should be reviewed. The physician should ask whether factory workers wear appropriate protective clothing and whether contaminated shoes and clothing are left at the factory. In some cases, contaminated shoes and clothing might either be worn home or brought home for laundering, which allows take-home contamination. State and federal OSHA offices can provide information and assistance to reduce such workplace health concerns. The National Institute for Occupational Safety and Health (NIOSH) is another resource for workplace health information (Appendix D).
Before discharging the child from the hospital, the health care provider must ensure no possible mercury exposure exists at home (i.e., remediation has taken place). Because of the high risk for increased mercury absorption after chelation, this is especially important if the child received chelation therapy. As part of discharge planning, health care providers should share usable information and materials or provide informational resources to parents and caregivers on how to properly store and discard medications, batteries, tools (e.g., thermometers), disinfectants, and cooking and garden products, among others. Parents and caregivers can conduct their own environmental surveillance in the home. A checklist of possible contaminants and steps to take to prevent accidents that result in exposure is available for health care providers to distribute to parents and caregivers as part of anticipatory guidance practices (Table 6). Health care providers should also encourage parents and caregivers to keep the local poison control center number close to all telephones in the home (Appendix D).
Mercury exposure might have affected others in the same apartment building or community. If exposures resulted from take-home contamination, the homes of other workers also might be contaminated. If exposure resulted from a spill of the mercury taken by teenagers from their school chemistry lab, others might also be at risk. If the exposure resulted from old contamination of the loft building, other residents of that building are at risk. Public health officials should conduct evaluations to determine if other groups have actually been exposed. In addition, the industrial hygiene practices at the thermometer factory should be reviewed to ensure that they are adequate.
Young children are at particular risk from take-home as well as "in-home" contamination. A young child usually spends more time in the contaminated home compared to the parents and school-aged siblings. Also, mercury vapor is much heavier than air and tends to collect near the floor, where infants crawl, toddlers walk, and young children play, thus risking greater exposure to higher mercury air levels than are encountered by most adults.
Mercury can be found in breast milk, but levels of concern regarding infant toxicity have mainly been associated with maternal exposure to organic mercury compounds (e.g., methylmercury), not elemental mercury vapor. If levels of mercury in the mother's urine are normal, breastfeeding will probably pose no exposure hazard to the infant. If the mother's urine mercury levels are high, however, mercury levels in breast milk should be measured to ensure that they pose no risk to the infant. Breast milk mercury levels >4 µg/L exceed the safe intake level for an infant. Because breastfeeding is the optimal infant nutrition, the child health care provider should evaluate each case individually, after a careful physical examination of the child (although with low-level exposures, overt symptoms are unlikely), to determine whether the risks of breastfeeding outweigh the benefits. For more information about breastfeeding issues, see the AAP Handbook of Pediatric Environmental Health (Etzel and Balk 1999) chapter on human milk.
This teenage boy might be at increased risk of toxic mercury exposures for a number of reasons.
First, his proposed cleaning activities might involve extended contact with mercury-contaminated waste materials.
Second, part-time and temporary workers might not have an adequate opportunity to learn the proper use of personal protective equipment or might not fully understand or be aware of which hazardous substances to which they could be exposed at work and the health risks involved with such exposures.
Third, the typical sense of invulnerability in adolescents might reduce the boy's vigilance in the use of protective equipment and other measures to minimize exposure.
Fourth, the higher physical activity level of many teenagers might result in increased respiratory rate and volume and, therefore, greater inhalation exposures.
Fifth, an adolescent might be fascinated with mercury as a toy or object to show off to his friends and he might be tempted to take some home. As a result of increased risk of toxic mercury exposure, this teenager might exhibit neurologic effects similar to those seen in adults. In addition, he shares a similar risk of being the source of mercury take-home exposure to family members, who could include young children, by taking it home on his clothing, shoes, hair, and body.
