Table 1. Characteristics of the included studies.
| Study | Subjects | Exposure measurement | Matching variables | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Author | Year | Country | Study design | Cases* | Controls* | Age | Diagnosis | Year of diagnosis | Registry | Long-term measurement | Spot measurement | Calculated fields | Sex | Age | Geographic area |
| Savitz et al. | 1988 | USA | Matched case-control study | 128 | 207 | 0–14 years | Any childhood cancer | 1976–1983 | the Colorado Central Cancer Registry | √ | √ | √ | √ | ||
| Myers et al. | 1990 | UK | Matched case-control study | 374 | 588 | 0–14 years | Any childhood cancer | 1970–1979 | the Yorkshire Childhood Cancer Registry | √ | √ | √ | √ | ||
| London et al. | 1991 | USA | Matched case-control study | 162 | 143 | 0–10 years | Childhood leukemia | 1980–1987 | the Los Angeles County Cancer Surveillance Program | √ | √ | √ | |||
| Feychting and Ahlbom | 1993 | Sweden | Matched case-control study | 142 | 558 | 0–15 years | Any childhood cancer | 1960–1985 | the Swedish Cancer Registry | √ | √ | √ | √ | √ | |
| Olsen et al. | 1993 | Denmark | Matched case-control study | 1,707 | 4,788 | 0–15 years | Any childhood cancer | 1968–1986 | The nationwide cancer registration system | √ | √ | √ | |||
| Verkasalo et al.a | 1993 | Finland | cohort study | 29 | 1027 | 0–19 years | Any childhood cancer | 1970–1989 | √ | ||||||
| Preston-Martin et al. | 1996 | USA | Matched case-control study | 437 | 433 | 0–19 years | Childhood brain tumor | 1984–1991 | the Los Angeles portion of a multicenter | √ | √ | √ | √ | ||
| Linet et al. | 1997 | USA | Matched case-control study | 629 | 619 | 0–14 years | Childhood lymphocytic leukemia | 1989–1994 | the Children’s Cancer Group | √ | √ | √ | √ | ||
| Michaelis et al. | 1997 | Germany | Matched case-control study | 176 | 414 | 0–14 years | Any childhood cancer | 1991–1994 | the German Childhood Cancer Registry | √ | √ | √ | √ | ||
| Tynes et al. | 1997 | Norway | Matched case-control study | 532 | 2,112 | 0–14 years | Any childhood cancer | 1965–1989 | the Cancer Registry of Norway | √ | √ | √ | √ | ||
| Dockerty et al. | 1998 | New Zealand | Matched case-control study | 303 | 303 | 0–14 years | Childhood leukemia, brain tumor, other solid cancers | 1990–1993 | the New Zealand Cancer Registry | √ | √ | √ | |||
| Green et al. | 1999 | Canada | Matched case-control study | 189 | 381 | 0–14 years | Childhood leukemia | 1985–1993 | the Pediatric Oncology Group Registry | √ | √ | √ | √ | ||
| McBride et al. | 1999 | Canada | Matched case-control study | 399 | 399 | 0–10 years | Childhood lymphatic leukemia | 1990–1995 | In British Colombia and Quebec | √ | √ | √ | √ | ||
| UKCCS investigators | 1999 | UK | Matched case-control study | 2226 | 2226 | 0–14 years | Any childhood cancer | 1991–1996 | the UKCCS | √ | √ | √ | √ | ||
| Kleinerman et al. | 2000 | USA | Matched case-control study | 408 | 408 | 0–14 years | Childhood lymphoblastic leukemia | 1989–1993 | the Children’s Cancer Group | √ | √ | √ | √ | ||
| Bianchi et al. | 2000 | Italy | Matched case-control study | 101 | 412 | 0–14 years | Childhood leukemia | 1976–1992 | the National Electricity Board | √ | √ | √ | √ | √ | |
| Schüz et al. | 2001 | Germany | Matched case-control study | 514 | 1,301 | 0–14 years | Childhood leukemia | 1992–1994 | the German Childhood Cancer Registry (GCCR) | √ | √ | √ | √ | ||
| Foliart et al. | 2006 | USA | cohort study | 1–15 years | Childhood lymphoblastic leukemia | 1996–2004 | the Pediatric Oncology Group(POG) | √ | |||||||
| Kabuto et al. | 2006 | Japan | Matched case-control study | 312 | 603 | 0–15 years | Childhood leukemia | 1999–2001 | the 5 major children’s cancer study groups in Japan | √ | √ | √ | √ | ||
| Feizi and Arabi | 2007 | Iran, Tabriz | Matched case-control study | 0–14 years | Childhood leukemia | 1998–2004 | the Children’s Hospital of Tabriz | √ | √ | √ | √ | ||||
| Svendsen et al. | 2007 | Germany | cohort study | 1–14 years | Childhood lymphoblastic leukemia | 1988–1994 | √ | ||||||||
| Kroll et al. | 2010 | UK | Matched case-control study | 9695 | 9695 | 0–14 years | Any childhood cancer | 1962–1995 | the National Registry of Childhood Tumours | √ | √ | √ | √ | ||
| Malagoli et al. | 2010 | Italy | Matched case-control study | 46 | 184 | 0–13 years | Childhood leukemia | 1986–2007 | the Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) | √ | √ | √ | √ | ||
| Saito et al. | 2010 | Japan | Matched case-control study | 55 | 99 | 0–14 years | Childhood brain tumor | 1999–2002 | network of 107 hospitals | √ | √ | √ | √ | √ | |
| Does et al. | 2011 | USA | Matched case-control study | 0–8 years | Any childhood cancer | 2002–2007 | the Northern and Central California (NCCLS) | √ | √ | √ | √ | ||||
| Wünsch Filho et al. | 2011 | Brazil | Matched case-control study | 162 | 565 | 0–18 years | Childhood lymphocytic leukemia | 2003–2009 | Eight hospitals in the State of Sao Paulo | √ | √ | √ | √ | ||
| Jirik et al. | 2012 | Czech Republic | Matched case-control study | 79 | 79 | 0–14 years | Childhood leukemia | - | √ | √ | √ | √ | |||
| Ba Hakim et al. | 2014 | Malaysia | case-control study | 108 | 118 | 0–14 years | Childhood leukemia | 2001–2007 | University Kebangsaan Malaysia Hospital and Kuala Lumpur General Hospital | √ | |||||
| Bunch et al. | 2015 | UK | Matched case-control study | 52,525 | 52,525 | 0–14 years | Any childhood cancer | 1962–2008 | the national registry of childhood tumours (NRCT) | √ | √ | √ | √ | ||
| Pedersen et al. | 2015 | Denmark | Matched case-control study | 3,277 | 9,129 | 0–14 years | Childhood leukemia, lymphoma, brain tumor | 1968–2003 | the Danish Data Protection Agency | √ | √ | √ | √ | ||
| Salvan et al. | 2015 | Italy | Matched case-control study | 412 | 587 | 0–10 years | Childhood leukemia | 1998–2001 | the SETIL case-control study | √ | √ | √ | √ | ||
| Kheifets et al. | 2017 | USA | Matched case-control study | 5,788 | 5,788 | 0–15 years | Childhood leukemia | 1986–2008 | the California Cancer Registry | √ | √ | √ | |||
| Crespi et al. | 2019 | USA | Matched case-control study | 4,879 | 4,835 | 0–14 years | Childhood leukemia | 1986–2008 | the California Cancer Registry | √ | √ | √ | √ | ||
a: case control data generated from the original cohort by original author
*: Numbers of cases and controls presented in the table are for subjects with available measurements