Environmental Health: Dioxins and cancers

Environmental Health: Dioxins and cancers

TCDD, a type of PCDD substance, is recognized as the most toxic, with chlorine typically present in PCDD. Higher numbers indicate greater toxicity. In the 1980s, exposure to TCDD occurred among workers due to accidents or occupational exposure. Measurements showed TCDD concentrations 10 to 100 times higher than typical daily exposure, particularly in industrial workers. Epidemiological studies, including occupational cohorts from the United States, Netherlands, and Germany, as well as studies on factory workers and residents affected by incidents such as the Seveso disaster, highlight the carcinogenicity of TCDD.

 

<What are dioxins? (1) >

 

■   All cancers

Occupational cohort studies conducted in the United States, Germany, the Netherlands, and by the International Agency for Research on Cancer (IARC) have shown an increased risk of all cancers. Meta-analyses indicate that exposure to dioxins, including TCDD, raises the risk of death from all cancers (1). The Seveso disaster in Italy, where regions were categorized based on TCDD concentration, revealed elevated cancer risks in highly exposed areas. Studies on residents of these areas showed a slight increase in cancer risk, with significant increases in cancer mortality observed over longer periods. Follow-up studies on women living in the Seveso area also demonstrated a correlation between TCDD exposure and increased cancer mortality rates (2, 3).

 

■    Lung cancer

The U.S. NIOSH cohort study involved 5,172 workers from 12 plants. Serum TCDD levels averaged 233 pg/g lipid among 253 cohort members, compared to 7 pg/g lipid in unexposed individuals. Among exposed workers for more than 1 year, TCDD levels averaged 418 pg/g lipid in 119 workers. A follow-up study over 6 years found that as TCDD exposure increased, the standardized risk of lung cancer death rose by 1.06 times (SMR=1.06, 95%CI=0.88-1.26). Workers who developed chloracne rash due to TCDD exposure had a 1.45 times higher risk of lung cancer death (SMR=1.45, 95%CI=0.98-2.07), though statistically insignificant (4). Cumulative TCDD exposure showed a significant trend, with higher exposure linked to increased standardized mortality ratios for lung cancer (p trend=0.05). After 15 years, the relative risk of lung cancer significantly increased in the 6th quartile of TCDD exposure (HR=2.55, 95%CI=1.29-5.03). Following the Seveso incident, lung cancer death risk in exposed area A rose by 26% compared to the control area but was not statistically significant (RR=1.26, 95%CI=0.70-2.29). Most lung cancer deaths occurred within 15 years post-explosion, with a 60-70% increased risk, though statistically insignificant (2)

 

■    Other cancers

In a case-control study in Umeå, Sweden, the use of phenoxy or chlorophenol preparations was linked to soft tissue sarcomas, with an initial report in 1979. The IARC International Cohort Study spanning from 1939 to 1992 involving 21,863 workers found a doubled risk of death from soft tissue sarcoma in those exposed to herbicides containing dioxins (5). The U.S. NIOSH cohort study showed 2.32 times increase in standardized mortality ratio for soft tissue sarcomas, particularly significant in those who developed chloracne. A cohort study at the Dow Chemical plant reported a 4.1 times higher standardized mortality ratio for soft tissue sarcoma due to TCDD exposure (6).

Non-Hodgkin lymphoma risk increased in occupational cohort studies and the Seveso community, though most were not statistically significant. Case-control studies nested within IARC international cohorts showed a higher relative risk for non-Hodgkin's lymphoma in groups exposed to phenoxy herbicides, dioxin, and furan (7). The German Hamburg Cohort Study observed a standardized mortality ratio of 7.11 for non-Hodgkin lymphoma, particularly high in workers with over 20 years of exposure (8).

 

■    References

The content is primarily based on Polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans).

(1)     USEPA. Dioxins: https://www.epa.gov/trinationalanalysis/dioxins. Access date: 2024-0307

(2)     Crump, K. S., Canady, R., & Kogevinas, M. (2003). Meta-analysis of dioxin cancer dose response for three occupational cohorts. Environmental health perspectives, 111(5), 681-687.

(3)     Consonni, D., Pesatori, A. C., Zocchetti, C., Sindaco, R., D'Oro, L. C., Rubagotti, M., & Bertazzi, P. A. (2008). Mortality in a population exposed to dioxin after the Seveso, Italy, accident in 1976: 25 years of follow-up. American journal of epidemiology, 167(7), 847-858.

(4)     Warner, M., Mocarelli, P., Samuels, S., Needham, L., Brambilla, P., & Eskenazi, B. (2011). Dioxin exposure and cancer risk in the Seveso Women’s Health Study. Environmental health perspectives, 119(12), 1700-1705.

(5)     Steenland K, Piacitelli L, Deddens J et al. (1999). Cancer, heart disease, and diabetes in workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Journal of the National Cancer Institute, 91, 779–786. doi:10.1093/jnci/91.9.779

(6)     Kogevinas M, Becher H, Benn T et al. (1997). Cancer mortality in workers exposed to phenoxy herbicides, chlorophenols, and dioxins. An expanded and updated international cohort study. American Journal of Epidemiology, 145, 1061– 1075. PMID:9199536

(7)     Collins, J. J., Bodner, K., Aylward, L. L., Wilken, M., & Bodnar, C. M. (2009). Mortality rates among trichlorophenol workers with exposure to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin. American journal of epidemiology, 170(4), 501-506

(8)     Kogevinas M, Kauppinen T, Winkelmann R et al. (1995). Soft tissue sarcoma and non-Hodgkin’s lymphoma in workers exposed to phenoxy herbicides, chlorophenols, and dioxins: two nested case-control studies. Epidemiology, 6, 396–402. PMID:7548348

(9)     Becher H, Flesch-Janys D, Kauppinen T et al. (1996). Cancer mortality in German male workers exposed to phenoxy herbicides and dioxins. Cancer Causes Control, 7, 312–321. doi:10.1007/BF00052936 PMID:8734824