HEALTH CONSULTATION

DOBBINS AND 55th AVENUE

HUDSON FARM NITRIC ACID RELEASE
LAVEEN, MARICOPA COUNTY, ARIZONA

BACKGROUND

The Arizona Department of Health Services (ADHS) was asked by the Arizona Department ofEnvironmental Quality (ADEQ) to evaluate the potential health effects from inhalation of toxicvapors as a result of an unplanned, concentrated nitric acid release. ADHS was asked what typesof health effects the nearby communities may experience from the nitric acid, and what follow upmeasures would be necessary to ensure public health and address the community concerns.

According to Hudson Farms, at approximately 1 pm on July 1st, concentrated nitric acid beganescaping from a small leak in a 33,000 gallon storage tank on private property located at Dobbinsand 55th Avenue in Laveen. By 4:30 pm, the first responding fire department units observed anorange colored plume that was moving with the wind direction. [see attachment A for plumemaps] The large plume continued to dissipate throughout the area until about 8:30 pm that night. Small amounts of nitric acid that was generally restricted to the Hudson property continued toleak until approximately 8 am the morning of July 2nd when pumping of acid waste waters intoemergency storage tanks was completed. It is estimated by ADEQ that a total of 4,000-4,500gallons of concentrated nitric acid was released from the storage tank.

Approximately 600 people from the town of Laveen and the Gila River Indian Community wereimmediately evacuated [see attachment B for evacuation area]. Due to the nitric acid clouddispersion, the Phoenix Fire Department evacuated all residences in the town of Laveen and theGila River Indian Reservation that were in the path of the plume, and thus had the greatest chancefor exposure. Residents were evacuated to Cash Elementary School and some local hotels. ADHS counseled residents on site at the elementary school at approximately 11 pm that eveningabout potential health effects of nitric acid exposure. Red Cross nurses were also at the school totreat victims and offer other emergency services. Residents were allowed re-entry to their homesthe following day, July 2nd at approximately 10 am.

Due to safety considerations no ambient air samples were collected in the plume during the periodwhen large amounts of nitric acid were being released. The ADEQ sampled ambient air forconcentrated hydrochloric and nitric acids downwind of the release only after the massive releaseof nitric acid had ceased. Samples collected by the ADEQ downwind of the release between 6 pmand 9 pm revealed trace amounts of both acids were detected in Draeger tubes. Air monitoringsamples were collected between 1 am and 2:30 am at eight locations downwind of the release todetermine whether it was safe to lift the evacuation of area residents. None of the air samplescontained nitric acid above detectable limits.

The sampling results are summarized in Table 1. [ADEQ Emergency Response Report on Hudson Farms, July 1998].

**trace means <1ppm (not measurable, but Draeger tube showed a visually detectible color change) [ADEQ HAZMAT Report,1998]

In order to address community concerns, on the morning of July 2nd, prior to residents re-entering the neighborhood, various residences at the nearby neighborhoods were tested for aciditywith a pH indicator strip test [See attachment D for map of sampling area]. Four or five samples were taken inside and outside of seventeen homes to determine whether any acid residuesremained. Samples were taken on evaporative cooling pads, in window sills, on A/C ducts,kitchen counters, and various other locations inside and outside of homes [Laidlaw Report, 1998]. All of the areas tested indicated a pH of 7 or 8, showing no acid present.

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