Table 4.

Summaries of studies on non-specified HAB aerosols and health (n = 3).

Author and year	Location	Exposure assessment method	Population and study period	Measured outcome	Findings summary
Lavery 2021a	USA	ICD-9 and ICD-10 codes for HAB exposure	IBM MarketScan Research Databases, which contain de-identified healthcare claims data for individuals with commercial insurance and some Medicaid beneficiaries. Databases between January 2009 and April 2019	ICD-9 and ICD-10 health diagnostic codes that were associated with HAB exposure. Most frequent outcomes included cough, allergy, other malaise and fatigue, headache, routine general medical examination, shortness of breath, hypertension, acute pharyngitis, and acute upper respiratory infection.	380 records in the Commercial database and 178 records in the Medicaid database were identified. The most common ICD health code was for respiratory events. A large peak in HAB exposure code and respiratory events coincided with red tide event in the Gulf of Mexico High counts of respiratory events were also seen in East North Central region consisting of states by the Great Lakes, potentially coinciding with cyanobacterial HABs. Few records for neurological events such as headaches and dizziness (11.8%); eye or skin irritation (10.9%); or gastrointestinal events (5.7%).
Lavery 2021b	USA	ICD-9 and ICD-10 codes for HAB exposure; chief complaint text	National Syndromic Surveillance Program (NSSP) for HAB exposure–associated administrative discharge diagnosis codes and chief complaint text terms related to HAB exposure January 1, 2017–December 31, 2019.	Emergency department visits associated with HAB exposure	n = 321 harmful algal bloom–associated ED visits were identified, with ED visits increasing in summers. Among these visits, 106 (33%) were identified through ICD-10 codes only; the addition of chief complaint text key terms to the query identified an additional 215 (67%) visits. Primary syndrome categories among the ED visits were respiratory (41.4%); gastrointestinal (13.7%); neurologic (10.3%); and dermatologic (8.4%).
Roberts 2020	18 states in USA that adapted the One Health Harmful Algal Bloom System (OHHABS)	Data reported to OHHABS included 421 HAB events. HAB events reported to CDC are classified based on standard definitions: -Suspected HAB events: observational/environmental data or associated illness. -Confirmed HAB events: either laboratory-based testing or both observational/environmental data and at least one associated case of illness. -Suspected human/animal cases: HAB exposure and signs/symptoms. -Probable human/animal cases: observational/environmental data, laboratory-based HAB data, or a professional medical diagnosis. -Confirmed human/animal cases: one of clinical data confirming exposure plus a professional diagnosis, or laboratory-based HAB data plus a professional diagnosis.	A total of 389 human cases of illness, with 341 (88%) classified as probable, and at least 413 animal illnesses were reported between 2016 and 2018.	Reported symptoms (e.g., gastrointestinal, generalized, dermatologic, neurologic) were recorded, as well as time to onset for a subset of cases.	Data reported to OHHABS by 18 states for 2016–2018 included 421 harmful algal bloom events, 389 cases of human illness, and 413 cases of animal illness. Laboratory testing for 372 (88%) HAB events was performed. Toxin texts were done for 308 reports of HAB events (83%), which frequently identified microcystins (94%), followed by anatoxin-a (10%) and saxitoxin (6%). 11% identified multiple toxins. The majority of HAB events occurred during May–October (98%), peaking in July (27%). The majority (89%) of the exposures involved fresh water. Most of HAB events were classified as confirmed (88%), while the majority of human illnesses were classified as probable (87%), and animal illnesses as suspected (81%). Most frequent symptoms were (67%); generalized (43%); dermatologic (27%); or ear, nose, or throat-related (16%) symptoms. Time to onset of initial signs or symptoms was available for 124 persons who had a one-time exposure and ranged from 1 min to 8 days. No mortality cases were reported.