The committee responsible for VAO found that there was inadequate or insufficient information to determine whether an association existed between exposure to the chemicals of interest (2,4-D, 2,4,5-T or its contaminant TCDD, picloram, or cacodylic acid) and leukemia. Additional information available to the committees responsible for Update 1996, Update 1998, and Update 2000 did not change that finding (see Table 6-49).

Burns et al. (2001) reported data on a cohort of 1,517 male workers involved in the manufacture or formulation of 2,4-D in 1945–1994. A job–exposure matrix was developed to assign workers to exposure categories based on measurements of time-weighted average exposure. Mortality in the study cohort was compared with mortality for all white US males and for an internal reference population of nonexposed manufacturing workers in the same company (see Chapter 4 for study details). Mortality from leukemia in the entire cohort was similar to rates in all US males (four deaths; SMR = 1.3, 0.4 –3.3). Similar results were obtained in an analysis based on a 20-year induction period. In the comparison with nonexposed workers, an excess in lymphopoietic mortality was noted in workers with high-cumulative-dose exposure to 2,4-D (four deaths; RR = 2.1 for 0-year induction and 2.7 for 20-year induction). That subgroup of exposed workers did not experience deaths from non-Hodgkin's lymphoma but may have included deaths from Hodgkin's disease and MM in addition to leukemia.

Cancer incidence and mortality were assessed in a cohort of 504 forestry workers in Sweden who were characterized by presence or absence of exposure to phenoxy herbicides in 1954–1967 (Thörn et al., 2000; see Chapter 4 for study details). Follow-up for mortality was completed through 1994, and data on cancer incidence were available from 1958–1992. No cases of leukemia occurred in the exposed members of this cohort.

Revich et al. (2001) analyzed data on cancer incidence and mortality in Chapaevsk, a city of 83,000 residents in the Samara region of Russia. A number of industries are in Chapaevsk, and production at one major chemical plant appeared to be responsible for dioxin contamination that was documented in the air, soil, and water of the city. Mortality due to leukemia during the years 1995–1998 was compared with mortality in the Samara region as a whole; the SMR was 1.5 for both men and women (0.8–2.7 in men; 0.8–2.4 in women), on the basis of 11

Front Matter (R1-R18)

Executive Summary (1-11)

1. Introduction (12-19)

2. Considerations in Evaluating the Evidence (20-29)

3. Toxicology (30-102)

4. Overview of Epidemiologic Studies (103-214)

5. Exposure Assessment (215-241)

6. Cancer (242-392)

7. Reproductive and Developmental Effects (393-446)

8. Neurobehavioral Disorders (447-476)

9. Other Health Effects (477-522)

10. Research Recommendations (523-528)

Appendix A: Agendas of Public Meetings (529-530)

Appendix B: ICD-9 Codes for Health Outcomes of Interest (531-533)

Appendix C: Committee and Staff Biographies (534-538)

Index (539-620)