EPA — U.S. Environmental Protection Agency · Rate Limits

Epa Rate Limits

The U.S. EPA operates several distinct API surfaces, each with its own rate-limiting regime. The Air Quality System (AQS) Data Mart caps clients at 10 requests per minute with a recommended 5-second pause between calls and a per-query row ceiling. The Clean Air Markets (CAM) easey APIs enforce a per-key 1,000 requests/hour quota plus a 15-minute single-request timeout and 500-row page maximum. The Envirofacts REST data service does not publish an explicit per-second cap but rejects queries that fail to complete within 15 minutes. ECHO, FRS, ATTAINS, How's My Waterway, and most other open Envirofacts- fronted services are public and unauthenticated; reasonable use is expected. Several authenticated surfaces (Grants, FRS Submit, e-Manifest production) require credentials issued by EPA program offices and apply program-specific throttling.

Epa Rate Limits is the machine-readable rate-limit profile for EPA — U.S. Environmental Protection Agency on the APIs.io network, in the API Commons Rate Limits shape.

It captures 11 rate-limit definitions, measuring requests_per_minute, seconds_between_requests, rows_per_query, parameters_per_request, and requests_per_hour.

Limit state is signalled in the retryAfter and requestId response headers, and an exhausted limit returns HTTP 429.

This profile was written by API Evangelist and has not been verified against a page the provider published; treat every limit as unconfirmed until a dated transcription replaces it.

The profile also includes 6 backoff/retry policies defined and response codes documented for throttled, quotaExceeded, requestTimeout, and serviceUnavailable.

Tagged areas include Rate Limiting, Government, and Environmental.

11 Limits Exhausted: HTTP 429 Quota: 429 retryAfterrequestId
Method: generated, dated 2026-05-29.
Written by API Evangelist on 2026-05-29 and not verified against a page the provider published. Treat every limit as unconfirmed until a dated transcription replaces it.
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Rate LimitingGovernmentEnvironmental

Limits

AQS Data Mart — request rate account/key
requests_per_minute · minute
10
AQS documents a maximum of 10 requests per minute, with a 5-second recommended pause between requests; clients must await completion before submitting the next.
AQS Data Mart — interval between requests account/key
seconds_between_requests · second
5
Minimum 5-second pause between successive requests.
AQS Data Mart — per-query row ceiling query
rows_per_query
1000000
Queries returning more than 1,000,000 rows are discouraged and may be terminated.
AQS Data Mart — parameter codes per request query
parameters_per_request
5
Maximum of 5 AQS parameter codes per request.
Clean Air Markets (easey) — request rate account/key
requests_per_hour · hour
1000
Default per-key rate limit across all CAM streaming, emissions, facilities, accounts, and CAMD services.
Clean Air Markets (easey) — request timeout request
minutes_per_request · minute
15
A single CAM API request will time out after 15 minutes.
Clean Air Markets (easey) — page size query
rows_per_page
500
Maximum 500 rows per page for paginated CAM endpoints.
Clean Air Markets (easey) — streaming UI download request
rows_per_download
1000000
1,000,000 record maximum for streaming services UI downloads; programmatic API has no record cap.
Envirofacts Data Service — request timeout request
minutes_per_request · minute
15
Envirofacts queries that fail to complete within 15 minutes are aborted; use pagination to stream large result sets.
ECHO Web Services — query ID lifetime query
minutes_qid_valid · minute
30
ECHO get_facilities returns a query_id (QID) that is valid for roughly 30 minutes; subsequent get_qid / get_map / get_download calls must reference it within that window.
How's My Waterway, ATTAINS, FRS Query, e-Manifest, Insect Repellents, ELG Search IP
varies
not publicly documented
These public services do not publish a hard per-IP cap. Reasonable, well-behaved use is expected. Heavy scraping may be rate-limited at the edge by api.epa.gov or data.epa.gov.

Policies

ApiKeyRegistration
AQS requires email-based registration that returns a key by email. CAM requires a key requested via the CAM API Portal. api.data.gov fronts other EPA APIs with its standard X-API-Key sign-up flow (1,000 requests/hour default).
ExponentialBackoff
On 429 or timeout responses, retry with exponential backoff. The AQS docs recommend waiting for one request to complete before issuing the next; CAM recommends honoring Retry-After.
Pagination
Envirofacts pages via path-segment ranges (`1:100`). CAM streaming and v2 endpoints page via offset/limit query parameters. Always page large extracts rather than relying on a single oversize query.
BulkDownloads
For program-wide extracts, prefer the agency's bulk downloads (ECHO Exporter ZIPs, AQS pre-generated annual files, GHGRP downloads) over hammering the live APIs.
PrimacyAndStateData
Several program APIs reflect data forwarded from state primacy agencies; freshness varies by program (AQS data can lag 6+ months from collection).
AuthenticatedSubmissions
Submission APIs (FRS Submit, e-Manifest, Grants) are credentialed via NAAS/CDX and apply program-specific concurrency and throttling on a per-account basis.

Sources

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