Pesticide chemical ups non-Hodgkin lymphoma risk in Asians
There appears to be a positive and significant link between non-Hodgkin lymphoma (NHL) risk in Asians and blood concentration of β-hexachlorocyclohexane (β-HCH), an organochloride (OC) used in many pesticides, according to a new study.
“This [study] provides support that environmental exposure to HCH may be associated with risk of NHL and adds some evidence that β-HCH may itself be a carcinogen,” said researchers, however noting that other OCs, such as p,p’-dichlorodiphenyldichloroethylene (p,p’-DDE), have no such effect.
Recruiting from three prospective cohorts in Shanghai and Singapore, researchers conducted a case-control study of 167 NHL patients (mean age 57±7 years; 62 percent male) and 167 healthy controls (mean age 57±8 years; 62 percent male). Concentrations of p,p’-DDE were highest in both NHL patients (8,570 ng/g lipid) and controls (8,070 ng/g lipid). [Int J Cancer 2019;doi:10.1002/ijc.32350]
In comparison, the mean concentrations of β-HCH in NHL patients and controls were 5,670 and 5,480 ng/g lipid, respectively. Though some variations across the individual cohorts existed, concentrations were consistently and substantially higher in both Shanghai cohorts relative to the Singapore participants.
“Whereas the variation in the two Shanghai cohorts may reflect differences in the timing of blood collection, the substantially higher levels in Shanghai relative to Singapore likely reflect differences in external exposure,” researchers explained.
Despite potential differences in external exposure, the effect of β-HCH was consistent across all three cohorts. In the pooled analysis, the highest tertile of β-HCH concentration was significantly associated with a higher risk of NHL, either including cases of lymphoid leukaemia (odds ratio [OR], 1.8; 95 percent CI, 1.0–3.2; ptrend=0.049) or not (OR, 1.9; 1.0–3.5; ptrend=0.04). Heterogeneity was nonsignificant (p=0.88).
Moreover, similar findings were obtained even when analysis was restricted to the two Shanghai cohorts, and when additional adjustments for other OCs, such as polychlorinated biphenyl congealers, were performed. The relationship between β-HCH and NHL risk likewise remained consistent in patients diagnosed <7 and >7 years after blood collection.
No other OC pesticide tested had a significant interaction with NHL risk. Despite being much higher in the current Asian cohort relative to established values in Western populations, p,p’-DDE did not significantly increase the risk of NHL (highest vs lowest tertile: OR, 1.1; 0.6–1.8), nor did it exert an effect in the individual cohorts.
Subsequent analyses excluding lymphoid leukaemia or stratified according to time between blood collection and diagnosis did not change the null effect of p,p’-DDE.
“Our findings provide the first evidence suggesting associations between blood levels of β-HCH and NHL risk in a population in Asia,” said researchers.
“Although there is some limited evidence that [dichlorodiphenyltrichloroethane] is associated with NHL risk based on studies in Western populations, our findings among Asians do not support an association with levels of p,p’-DDE,” they continued.
“Further evaluation of these associations, particularly in understudied Asian populations that have OC exposure characteristics that differ from the West, would be informative to further our understanding of the lymphomagenic potential of these ubiquitous compounds,” researchers added.