The illnesses, from 2010, were the first in the U.S. caused by methyl bromide exposure in a produce storage area distant from where the fumigant was applied, according to the latest Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention.
It was applied to grapes imported from Chile through the Port of Long Beach. The U.S. Department of Agriculture requires methyl bromide fumigation to prevent infestation by the Chilean false red mite.
The Carson facility, unnamed in the report, is 6 miles from the port.
The inspectors — both men, ages 22 and 52 — complained of symptoms that included difficulty walking, dizziness and impaired memory, speech or vision. They were found to have elevated serum bromide levels.
The CDC said some measurements of single-instant methyl bromide levels in confined spaces at the Carson facility exceeded eight-hour exposure limits.
The report advises similar facilities to consider increased aeration time, reduced postfumigation exposure, reduction of packaging materials that might absorb methyl bromide or hinder aeration, and changes in pallet stacking to improve airflow. Companies should warn workers of potential health risks, the report says.
Investigators found that the Port of Long Beach had aerated fumigated grapes according to USDA standards.
Both inspectors told investigators their working conditions in Carson were unusual. They said they were required to work inside the refrigerated area, while elsewhere they had typically worked outside.
The 22-year old was a quality inspector at an unnamed wholesale produce shipping company. The older man was an independently contracted quality inspector. Later that year, both said they felt fully recovered. The 52-year-old returned to inspection work, while the younger man went to graduate school.
In April 2010, the Port extended aeration time from four to nine hours to reduce concentrations in semitrailer loads. Nevertheless, investigators testing shipments on arrival in Carson and 215 miles away in Tulare County found methyl bromide levels higher than had been sampled while the trailers were still at the port of entry.
“(O)ffgassing of the fumigant from the produce caused levels to increase to potentially hazardous concentrations,” according to the CDC report.
Ventilation seemed to reduce that risk, but the findings underscore that levels can rise or fall unexpectedly.