Children’s Environmental Health in Michigan
Childhood cancer is the second leading cause of death, after accidents, for children in the U.S. (Zahm, Devesa 1995; NCI 2009). The incidence of cancer in all sites combined among children ages 0-19 increased by 22% from 13.8 per 100,000 in 1973 to 16.8 per 100,000 in 2000 and most of this increase occurred in the1970s and 1980s (Clapp, 2005)
According to Clapp, et. al, “The growing burden of cancer on children may provide some of the most convincing evidence of the role of environmental and occupational exposures in causing cancers. Children do not smoke, drink alcohol, or have stressful jobs. In proportion to their body weight, however, “children drink 2.5 times more water, eat 3 to 4 times more food, and breathe 2 times more air than adults” (Clapp, 2005).
Epidemiologic studies have linked childhood leukemia and childhood brain and central nervous system cancers with parental and childhood exposure to solvents, pesticides, petrochemicals, radiation, and certain industrial by-products (namely dioxins and polycyclic aromatic hydrocarbons) (Clapp, 2005). The incidence of childhood leukemia and brain cancer has been rising steadily in the past decade (Clapp et al. 2007).
Carcinogenesis is the result of multiple mutations in a cell that affect cell growth, mitosis, and regulation. There are many causes of mutations and many means by which cancer may develop including an increase in the expression of protooncogenes (early genes that may lead to cancer); decreased expression of tumor suppressor genes; and chromosomal instability.
Much remains to be learned about the associations between environmental factors and childhood cancers due to the relative infrequency of the disease and to difficulties in accurately assessing environmental exposures (Gufferman 1998; Robison et al. 1995).
Further research is needed to better understand the relationship between environmental factors and the incidence of childhood cancer. The National Children’s Study may shed light on this question over time.
The carcinogens discussed in this wiki include those with the most robust data supporting an association: ionizing radiation, solvents (benzene, perchlorate, and trichloroethylene), pesticides, second hand smoke, and dioxins. Non-ionizing radiation, and other chemicals with limited evidence linking them to childhood cancer are beyond the scope of this wiki at this time.
This section will briefly summarize exposures and associated health effects, present leading policy practices from other states, and recommend steps to minimize childhood exposure in Michigan.
Childhood Cancer in the United States
Childhood cancer claims the lives of roughly 1,500 children in the United States each year, and it is the second leading cause of death, after accidents, for children in the U.S. (Zahm, Devesa 1995; NCI 2009). Childhood cancer incidence is highest amongst children aged 0-4 and 15-19 years old (Zahm, Devesa 1995; Children’s Oncology Group 2005), a statistic that suggests environmental exposures occurring prenatally may be of importance for cancer etiology. Boys are more likely than girls to be diagnosed with cancer (Zahm, Devesa 1995). In the U.S., incidence rates are higher for acute lymphocytic leukemia than for any other site-specific cancer (Figure 1).
Overall incidence of childhood cancers in the U.S. has gradually increased since the mid-1970s (Figure 2).
Childhood Cancer in Michigan
There are limited data on childhood cancer incidence and mortality trends in Michigan, according to the National Cancer Institute SEER data (NCI 2009). For example, specific incidence rates of all childhood cancers in children age <15 years are available for only 22 of Michigan’s 83 counties (NCI 2009). Of those, all but five are at or above the U.S. average incidence rate of 15.2 per 100,000 for the period 2001-2005. The Michigan average is 16.1 per 100,000 for this time period (NCI 2009). Figure 3 shows the cancer incidence rate for Michigan by county.
† Incidence rates (cases per 100,000 population per year) are age-adjusted to the 2000 US standard population (19 age groups: <1, 1-4, 5-9, ... , 80-84, 85+). Rates are for invasive cancer only (except for bladder cancer which is invasive and in situ) or unless otherwise specified. Rates calculated using SEER*Stat. Population counts for denominators are based on Census populations as modified by NCI. The US populations included with the data release have been adjusted for the population shifts due to hurricanes Katrina and Rita for 62 counties and parishes in Alabama, Mississippi, Louisiana, and Texas. The 1969-2007 US Population Data File is used for SEER and NPCR incidence rates.§ Data not provided because it did not meet USCS publication standards for one or more years during the rate period of data collection. American Cancer Society's Facts & Figures provides estimates of numbers of new cancer cases and deaths.# Data do not include cases diagnosed in other states for those states in which the data exchange agreement specifically prohibits the release of data to third parties.* Data has been suppressed to ensure confidentiality and stability of rate estimates. Counts are suppressed if fewer than 16 cases were reported in a specific area-sex-race category.
As with overall rates for the U.S., mortality rates from all childhood cancers in Michigan fell from 1981 to 2005 (Figure 4).
The State of Michigan Cancer Surveillance Program provides county-specific incidence rates for children aged 19 and under. These rates are presented in Figure 6 below.
Counties reporting fewer than six cases were considered to have unreliable incidence rates and therefore were not included in the report. When considering the counties for which reliable incidence rates were calculated, the highest incidence rates were observed in Bay, Monroe, and Grand Traverse counties (Figure 6). These rates are considerably higher than the overall rate of 17.0 cases per 100,000 for the state of Michigan in 2004 and also higher than the incidence rates for all U.S. children of the same age range (Figure 1). As a whole, Michigan’s cancer incidence rate for the observed time frame is slightly elevated over the U.S. average.
Clapp RW, Howe GK, Jacobs MM. 2005. Environmental and Occupational Causes of Cancer: A Review of Recent Scientific Literature. Lowell Center for Sustainable Production. Accessed at: http://www.sustainableproduction.org/proj.envh.canc.causes.shtml.
Children’s Oncology Group. 2005. CureSearch. http://www.curesearch.org/our_research/index_sub.aspx?id=1475
Gufferman S. 1998. Methodologic approaches to studying environmental factors in childhood cancer. Environmental Health Perspectives 106(Suppl 3):881-886.
Michigan Cancer Incidence File. 2006. Data processed by the Michigan Department of Community Health, Vital Records and Health Data Development Section, December 15, 2006.
National Cancer Institute (NCI) 2009. State Cancer Profiles. #.
State Cancer Profiles. 2011. Accessed on May 17, 2011. #
United States Cancer Statistics Working Group. United States Cancer Statistics: 1999–2004 Incidence and Mortality Web-based Report. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Cancer Institute; 2007. Available at: www.cdc.gov/uscs.
Zahm SH, Devesa SS. 1995. Childhood cancer: overview of incidence trends and environmental carcinogens. Environmental Health Perspectives 103(Suppl 6): 177-184.