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Several residential areas were likely to be impacted by the movement of the plume, and aninvestigation was conducted to collect self reported health complaints. Three communities weretargeted. Figure 1 displays the borders of this area. A small residential neighborhoodapproximately 100 yards southwest of Hudson Farms was surveyed on July 6, 1998 by ADHSstaff. All sixty-four homes on five residential streets between 53rd Avenue and 55th Avenue,adjacent to Hudson Farm were approached by staff from the Office of Environmental Health. Asecond subdivision of 27 homes southeast of the farm that was in the trail of the plume was alsosurveyed by ADHS the same day.

The Gila River Indian Community worked closely with ADHS to also conduct a random sampleinvestigation using the ADHS Acute Exposure Survey form [see attachment C]. The GilaEnvironmental Health program surveyed every fifth house on the reservation. The results of thecombined investigation are shown in Table 2.

Figure 1: Area of Residences Surveyed

If residents were home, they were asked to fill out a survey questionnaire asking whether theywere experiencing health symptoms that began during and after the release of nitric acid. Residents with symptoms were advised to consult with their primary care physician and the GoodSamaritan Poison Control Center to ensure proper diagnosis and treatment.

For the residents who were not home, an information packet was issued by ADHS advising thecommunity to be aware of the importance of seeking treatment for related symptoms. ADHSstaff received calls from 19 area residents that experienced health symptoms who were not homeduring our field investigation. The call-in data and reported health complaints are included inTable 2.

Table 2.

Health Symptoms Reported
 Street or Location No Symptoms Had
Sought medical attention Admitted to hospital Not home/ flyer only Total
  homes persons homes persons homes persons homes persons homes persons*    
Dobbins   21   4   0   0 2 7 9 32
La Mirada   10   18   0   0 7 25 15 53
Piedmont   10   14   7   0 7 25 16 49
McNeil   7   10   0   0 13 46 18 63
Olney   3   0   0   0 5 18 6 21
(on duty personnel)
  5   9   3   0 n/a     14
† Gila River 42 336 26 38
3 272 2176 ** 340 2550**
SE Community   18   18   7 0   17 60 27 95
Total   410   111   21   3 323 2357 431 2877

ADHS Call-In Complaints   3   16   10   1        
Hospital surveillance data       114   114   7        

* the average # of people per home is 3.5 people/home [1990 Census Tract Data]
** average persons per home in Gila = 8 people/home [Gila River Indian Community Survey, 1998]
† Gila River data courtesy of Eric Faisst, Gila River Indian Community

We made direct contact with 44% of the homes in the two neighborhoods targeted by ADHS(40/91). 20%(68/340) of the homes in the Gila River community were reached by environmentalinvestigators from the reservation. Additional data was gathered from local hospitals and clinics,and also from concerned residents calling ADHS to report health problems.

Several local hospitals and clinics were also contacted by ADHS to monitor the number ofpatients who presented with acute exposure symptoms, as well as to obtain the number of patientsadmitted for further observation and treatment. The local hospitals / clinics in close proximity tothe plume included Gila River Crossing Clinic, the Phoenix Indian Medical Center, ChandlerRegional Hospital, and Good Samaritan Hospital. Throughout the evacuation period, residentswere seen by nurses in the two emergency treatment centers set up by the American Red Cross atthe Cash Elementary School, and at the old Gila River Casino facility. If they needed additionalmedical attention, they were transferred to one of the area hospitals by the Red Cross. Refer toTable 3 for a summary of hospital and clinic reported data.

Table 3.

Area Hospitals & Clinics Reporting Cases
Facility Patients w/ possible exposure Treatment/ Dx / Hospitalization
Phoenix Indian Hospital 47 total=>
45 patients seen in ER=
2 respiratory distress==

=>water irrigation, albuterol/breathing therapy
Gila River Crossing Clinic


3 total =>
2 burning eyes, skin==

1 respiratory distress==


=>benadryl, water irrigation



Good Samaritan Hospital

41 total =>
21 information calls

20 direct exposure ===

=>Water irrigation of exposed areas, chest x-rays, albuterol therapy; No hospitalizations
Chandler Regional Hospital 2 total=>
1 shortness of breath==

1 burning throat & eyes======

=>hospitalized **

=>water irrigation
Red Cross @ Cash Elementary* 5 total=>
1 chest pain, throat irr=

4 shortness of breath,skin burning


=>water irrigation

Red Cross @ Gila River Casino* 16 total=>
2 chest pain, seizures=

14 sore throat, tearing,dizzy, skin irritation============

=>hospitalized ***

=>water irrigation, monitoring vitals signs

*emergency shelters & treatment centers staffed with RN's
** same patient transferred to Chandler Regional Hospital
*** same patients transferred to PIMC


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.

Trace levels of nitric acid and hydrochloric acid were present in air downwind of the release afterthe massive releases of nitric acid had occurred. The exact amount was not quantifiable, but thecolor change noted in the Draeger tubes with a minimum detection limit of 1 ppm suggests thepresence of the acids. No ATSDR Toxicological Profile for nitric acid exists, but data indicates athreshold limit value (TLV) of 2 ppm for HNO3, for a worker to be exposed without healtheffects. [CHRIS, 1998]. [TOMES: Meditext, 1998]. The TLV is an occupational standard thatis based upon an 8 hour exposure in relatively healthy workers. It is the only standard ofcomparison available in the literature, but it was not developed for use in the general populationand does not take into consideration sensitive subpopulations.

The TLV for HCL is 5 ppm. There are no reported health effects at an inhaled concentration of1ppm. While there are no serious health effects for inhalation at the levels detected duringenvironmental sampling, transient irritation to any exposed body parts may occur due to thecorrosive nature of the acids.

Nitric acid is a colorless liquid that when heated may produce red, toxic oxides of nitrogen (NOx)such as nitrogen dioxide (NO2), nitric oxide (NO), and the nitrogen dioxide dimer, which isnitrogen tetroxide (N2O4) . When exposed to water, nitric acid converts to form nitrogen dioxide(NO2), that upon hitting any surface reacts and converts back to nitric acid (HNO3). HCL in thepresence of water reacts to form chlorine gas, an irritating vapor, in an exothermic reaction[Meditext, 1998]. [CHRIS database: Chemical Reactivity, 1998].

Temperatures and other environmental conditions at the time of the release are likely to havefacilitated the transformation of nitric acid to nitrogen oxides. The temperature around the timeof the release was 39 degrees Celsius, and the relative humidity averaged about 35% and was ashigh as 54% in the early morning hours of July 2nd. [ADEQ Meteorology Report, 1998]. Moreover, the plume was visibly red, indicative of the presence of NO2. However, no airmonitoring data is available on any of the other compounds formed by oxidation of the acids.

It is likely that inhaled NO2 reacts with intrapulmonary water to re-form nitric and nitrous acidscausing metabolic acidosis [Lipsett, 1992]. Acids denature proteins, and in respiratory tissue,NO2 causes the formation of highly reactive free radicals that will further cause the oxidation ofunsaturated fatty acids. Multiple scenarios of systemic toxic mechanisms are possible, but withoutknown air concentrations of the nitrogen oxides, no dose based evaluation can be established.

Many of the symptoms reported in the literature from mild nitrogen oxide (NOx) exposure arenonspecific, transient symptoms including "dyspnea, cough, headache, fatigue, nausea, vertigo,and somnolence, which may persist up to two weeks without significant clinically detectiblepulmonary findings" on a chest x-ray. Severe exposures in individuals can present in symptoms ofchest pain, wheezing, diaphoresis, palpitations, pulmonary edema, and chemical pneumonitis[Lipsett, 1992].

The symptoms reported by residents during the health survey conducted by the ADHS and theGila River Indian community teams were consistent with the symptoms of HNO3 and NOxexposure in the literature. 241 residents reported experiencing some symptoms including cough,irritation of eyes, nose, throat, headaches, skin rashes, nausea, and dizziness. 60% of residentswho experienced symptoms sought medical intervention (145/241). Eleven of the 241 peopleexperiencing symptoms, or about 5%, were hospitalized due to serious symptoms that includedchest pain, seizures, pharyngitis, shortness of breath, excess cough, as well as the other acute symptoms noted above.


Children are more likely to be sensitive to the effects of nitric acid exposure due to theirdeveloping systems and their low body weight, but no evidence of the dose specific health effectsexists at this time. The only reference level that exists is an occupational standard that is based onhealthy workers. As such, the TLV is not an appropriate standard of comparison.

At the levels of nitric acid that were measured in the air, children and the elderly may haveexperienced more health effects than the adults. Several children and elderly reported healthsymptoms and were admitted to the hospital. While the health recommendations for follow upcare are the same for both children and adults, without specific concentrations of NOx in the air,no dose specific evaluation can be made.

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