Abstract
We identified hospital visits with reported exposure to harmful algal blooms, an emerging public health concern because of toxicity and increased incidence. We used the World Health Organization’s International Classification of Disease (ICD) medical code specifying environmental exposure to harmful algal blooms to extract hospital visit records in New York State from 2008 to 2014. Using the ICD code, we identified 228 hospital visits with reported exposure to harmful algal blooms. They occurred all year long and had multiple principal diagnoses. Of all hospital visits, 94.7% were managed in the emergency department and 5.3% were hospitalizations. As harmful algal bloom surveillance increases, the ICD code will be a beneficial tool to public health only if used properly.
A harmful algal bloom (HAB) is an excessive aquatic growth of cyanobacteria or marine algae that may produce toxins.1 Increases in nutrient runoff, water temperature, and eutrophication of fresh and marine surface waters have led to concerns about the increasing incidence of HABs.2 HABs and the toxins they produce, such as microcystins and cylindrospermopsins, have the potential to cause human illness.3,4 HAB exposure can occur through dermal contact, ingestion, or inhalation.5 Exposure can result in a variety of symptoms, including dermal irritation, gastroenteritis, and respiratory irritation. Many states have begun to implement HAB-associated illness surveillance systems in response to this emerging public health issue. However, these systems are generally based on passive reporting of symptoms by the general public and not necessarily on direct reporting by health care providers.6,7
The World Health Organization’s International Classification of Diseases (ICD) is a diagnostic tool that can be used by epidemiologists and health care professionals to assess health status.8 The ninth revision of the ICD, called the ICD-9, includes external cause-of-injury codes (E-codes) that provide information about causal circumstances leading to injuries and poisonings. In 2007, an E-code, E928.6, was implemented to specify exposure to harmful algae and toxins.9 To date, no literature has used this code to assess the extent of HAB-associated illnesses in the United States.
HABs have occurred in both inland lakes and coastal areas in all geographic regions of New York State, and are a potential source of exposure for anyone using affected waters.10 We assessed the utility of ICD-9 E-code E928.6 as a tool to enhance existing HAB-associated illness surveillance systems.
METHODS
We extracted hospitalizations and emergency department visits (referred to here as “hospital visits”) with the ICD-9 E-code E928.6 from the New York Statewide Planning and Research Cooperative System, a hospital-based administrative database that collects information on hospital visits in New York State. Hospital-based administrative databases are often used for environmental public health surveillance purposes to better understand spatial and geographic trends in the occurrence of diseases and other illness. The data set used in this analysis included hospital visits for the years 2008 through 2014 (the code was introduced in 2007).
Variables that we examined included age, gender, month and year of hospital admission, patient discharge status, and principal diagnosis codes. ICD-9 principal diagnosis codes provide the diagnosis that was primarily responsible for the hospital visit.
We used American Community Survey 5-year estimates for 2008 through 2012 to compare the demographic characteristics of the study group with those of the New York State population. We assessed the statistical significance of demographic comparisons (i.e., age, gender, and race/ethnicity) using the χ2 test. We analyzed data with SAS version 9.3 (SAS Institute Inc, Cary, NC) and the PROC FREQ procedure, which is used for tabulating the data.
RESULTS
We identified a total of 228 hospital visits with reported HAB exposure from 2008 to 2014 in New York State (Table 1). During this period, there was an average of 31 hospital visits per year with reported HAB exposure, ranging from 21 (in 2011) to 42 (in 2013) (data not shown). Hospitalizations made up a small overall percentage (5.3%) of all hospital visits. Hospital visits were reported during all months of the year (Figure 1).
TABLE 1—
Characteristics of Hospital Visits With An External Cause-Of-Injury Code for “Exposure to Harmful Algae and Toxins”: New York State, 2008–2014
| Variable | % Hospital Visits With Reported HAB Exposure (n = 228) | % Total NYS Populationa (n = 19 398 125) | P |
| Age group, y | < .001 | ||
| < 18 | 21.1 | 16.3 | |
| 18–24 | 13.2 | 10.2 | |
| 25–44 | 35.1 | 27.2 | |
| 45–64 | 25.0 | 26.7 | |
| ≥ 65 | 5.7 | 13.6 | |
| Gender | .22 | ||
| Female | 44.3 | 48.4 | |
| Male | 55.7 | 51.6 | |
| Race/ethnicityb | .02 | ||
| Non-Hispanic White | 50.8 | 58.2 | |
| Hispanic White | 7.8 | 7.8 | |
| Non-Hispanic Black | 22.3 | 14.4 | |
| Hispanic Black | 0.0 | 1.2 | |
| Non-Hispanic other | 8.8 | 9.6 | |
| Hispanic other | 10.4 | 8.7 | |
| Most common principal diagnosis categoriesc | |||
| Other effects of external causes | 12.3 | … | |
| Contact with and (suspected) exposure to other potentially hazardous chemical | 7.9 | … | |
| Toxic effect of carbon monoxide | 7.0 | … | |
| Superficial injury of cornea | 4.4 | … | |
| Allergy, unspecified | 4.4 | … | |
| Contusion of eye, unspecified | 2.6 | … | |
| Other and unspecified superficial injuries of eye | 2.2 | … | |
| Toxic effect of chlorine gas | 2.2 | … | |
| Patient discharge status | |||
| Discharge to home or self-care | 97.4 | … | |
| Otherd | 2.6 | … |
Note. HAB = harmful algal bloom; NYS = New York State.
The percentages are estimates based on 2008–2012 data from the American Community Survey.
Because race/ethnicity was unknown for 15.4% of hospital visits, percentages are based on n = 193 for this analysis.
The principal diagnosis categories with 5 or more observations are reported here.
Other types of patient discharge status include the following: discharge or transferred to skilled nursing facility (n = 2), discharged or transferred to a designated cancer center (n = 1), left against medical advice (n = 3).
FIGURE 1—
Mean Number of Inpatient and Outpatient Hospital Admissions With External Cause-of-Injury Codes for “Exposure to Harmful Algae and Toxins,” by Month: New York State, 2008–2014
Most patients (97.4%) were discharged to home or self-care. The most common individual ICD-9 primary diagnoses included the following: effects of external causes (12.3%), contact with potentially hazardous chemicals (7.9%), toxic effect of carbon monoxide (7.0%), superficial injury to the cornea (4.4%), unspecified allergy (4.4%), unspecified contusion of eye (2.6%), other and unspecified superficial injuries of eye (2.2%), and toxic effect of chlorine gas (2.2%). Compared with the estimated total population of New York State, those with reported HAB exposure tended to be younger (P < .001) and non-Hispanic Black (P = .02).
DISCUSSION
This analysis presents demographic and basic diagnosis information about patients whose hospital visit resulted in a code with reported HAB exposure. HABs are an emerging issue, and to better understand their public health burden, additional surveillance and research will be needed to investigate the incidence, risk factors, and clinical presentation of HAB-associated illnesses. However, the analysis of this code identified 2 concerns that should be explored in future studies.
First, exposures to HABs in New York State would be most likely during warmer months (June through August).9 The fact that hospital visits with HAB exposure were reported during the colder months, when HABs are rare (November through April), suggests that there may be either errors in record coding or other forms of exposure to HABs (e.g., travel to a location where HABs are present, cyanobacteria health food supplements). The other issue is that whereas diagnoses involving contact with potentially hazardous chemicals, superficial injury to the cornea, and unspecified allergy could potentially represent diagnoses associated with HAB exposure, it is unclear how other reported diagnoses, such as the toxic effects of carbon monoxide and chlorine gas, would be associated with HAB exposure.
Using available administrative data, we have provided an initial assessment of the utility of ICD-9 external cause-of-injury code E928.6 in public health surveillance for HAB-associated illness. Although the 2 causes for concern highlighted here suggest that caution is warranted in using this code for tracking HAB-related illness, the lack of more detailed clinical data limits our ability to make firm conclusions about the validity of the HAB exposure. Therefore, although this code provides a potential tool for public health professionals to track HAB-related hospital visits, more work is needed to confirm its usefulness.
ACKNOWLEDGMENTS
This study was supported in part by an appointment to the Applied Epidemiology Fellowship Program (to M. Figgatt) administered by the Council of State and Territorial Epidemiologists and funded by the Centers for Disease Control and Prevention (Cooperative Agreement 1U38OT000143-03).
We thank Virginia Roberts and Michele C. Hlavsa of the Waterborne Disease Prevention Branch of the Centers for Disease Control and Prevention for support and guidance.
HUMAN PARTICIPANT PROTECTION
No institutional review board approval was necessary for this study because it was classified as a surveillance and evaluation activity.
REFERENCES
- 1.Backer L, McGillicuddy DJ. Harmful algal blooms at the interface between coastal oceanography and human health. Oceanography (Wash D C) 2006;19(2):94–106. doi: 10.5670/oceanog.2006.72. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Anderson DM, Glibert PM, Burkholder JM. Harmful algal blooms and eutrophication: nutrient sources, composition, and consequences. Estuaries. 2002;25(4):704–726. [Google Scholar]
- 3.Manganelli M, Scardala S, Stefanelli M et al. Emerging health issues of cyanobacterial blooms. Ann Ist Super Sanità. 2012;48(4):415–428. doi: 10.4415/ANN_12_04_09. [DOI] [PubMed] [Google Scholar]
- 4.World Health Organization. International Classification of Diseases (ICD) Available at: http://www.who.int/classifications/icd/en. Accessed March 16, 2015.
- 5.Bernstein JA, Ghosh D, Levin LS et al. Cyanobacteria: an unrecognized ubiquitous sensitizing allergen? Allergy Asthma Proc. 2011;32(2):106–110. doi: 10.2500/aap.2011.32.3434. [DOI] [PubMed] [Google Scholar]
- 6.Wisconsin Dept of Health Services. Health concerns related to blue-green algae. May 20, 2015. Available at: https://www.dhs.wisconsin.gov/water/bg-algae/healthconcerns.htm. Accessed September 28, 2015.
- 7.Ohio Dept of Health. Harmful algal blooms: implications for tap/drinking water and recreational waters. September 8, 2015. Available at: https://www.odh.ohio.gov/odhprograms/eh/HABs/algalblooms.aspx. Accessed September 28, 2015.
- 8.Buck CJ. ICD-9-CM for Physicians. St. Louis, MO: Elsevier Saunders; 2013. p. 722. Vol. 1 and 2. Professional ed. [Google Scholar]
- 9.Hilborn ED, Roberts VA, Backer L et al. Algal-bloom associated disease outbreaks among users of freshwater lakes—United States, 2009–2010. MMWR Morb Mortal Wkly Rep. 2014;63(1):11–15. [PMC free article] [PubMed] [Google Scholar]
- 10.New York State Dept of Environmental Conservation. Archived blue-green algae notices. 2015. Available at: http://www.dec.ny.gov/chemical/83332.html. Accessed September 28, 2015.